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α‐Olefins are valued and abundant building blocks from fossil resources. They are widely used to provide small‐molecule or polymeric products. Despite numerous advantages of radical polymerization, it has been well‐documented as textbook knowledge that α‐olefins and their functionalized derivatives cannot be radically homopolymerized because of the degradative chain transfer side reactions. Herein, we report our studies on the homopolymerization of thiocyanate functionalized α‐olefins enabled by 1,4‐cyano group migration under radical conditions. By this approach, a library of ABC sequence‐controlled polymers with high molecular weights can be prepared. We can also extend this strategy to the homopolymerization of α‐substituted styrenic and acylate monomers which are known to be challenging to achieve. Overall, the demonstrated functional group migration radical polymerization could provide new possibilities to synthesize polymers with unprecedented main chain sequences and structures. These polymers are promising candidates for novel polymeric materials. [ABSTRACT FROM AUTHOR]

α‐Olefins are valued and abundant building blocks from fossil resources. They are widely used to provide small‐molecule or polymeric products. Despite numerous advantages of radical polymerization, it has been well‐documented as textbook knowledge that α‐olefins and their functionalized derivatives cannot be radically homopolymerized because of the degradative chain transfer side reactions. Herein, we report our studies on the homopolymerization of thiocyanate functionalized α‐olefins enabled by 1,4‐cyano group migration under radical conditions. By this approach, a library of ABC sequence‐controlled polymers with high molecular weights can be prepared. We can also extend this strategy to the homopolymerization of α‐substituted styrenic and acylate monomers which are known to be challenging to achieve. Overall, the demonstrated functional group migration radical polymerization could provide new possibilities to synthesize polymers with unprecedented main chain sequences and structures. These polymers are promising candidates for novel polymeric materials. [ABSTRACT FROM AUTHOR]

Anionic polyelectrolytes can be used for a variety of applications, including flocculation and enhanced oil recovery. While it is widely recognized that polyelectrolyte synthesis is impacted by the pre‐polymer formulation and polymerization conditions, the specific relationships between these factors and the subsequent polymer properties are not well understood. Therefore, the current work intends to improve understanding of ionic strength (IS) effects during the copolymerization of 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) and acrylamide (AAm). The aims of the study are i) to use in situ H1 NMR to study copolymerization kinetics, and ii) to determine how increasing IS impacts copolymerization kinetics (and, by extension copolymer microstructure). It is found that altering IS prior to copolymerization has significant impacts on the reactivity ratios, and therefore impacts the microstructure through multiple mechanisms. Increasing IS causes a crowding effect, where the propagating chain develops a random coil conformation and causes steric hindrance of the large AMPS monomer, decreasing the likelihood of AMPS propagation. When the IS is increased further, the ionic shielding effect is more impactful, increasing the likelihood of AMPS propagation. Ultimately, this work will make it possible to manipulate IS to synthesize AMPS/AAm copolymers with specific desirable properties for target applications. [ABSTRACT FROM AUTHOR]

Block copolymers, comprising polyether and polyolefin segments, are an important and promising category of functional materials. However, the lack of efficient strategies for the construction of polyether‐b‐polyolefin block copolymers have hindered the development of these materials. Herein, we propose a simple and efficient method to obtain various block copolymers through the copolymerization of epoxides and acrylates via bimetallic synergistic catalysis. The copolymerization of epoxides and acrylates proceeds in a sequence‐controlled manner, where the epoxides‐involved homo‐ or copolymerization occurs first, followed by the homopolymerization of acrylates initiated by the alkoxide species from the propagating polymer chain, thus yielding copolymers with a block structure. Notably, the high monomer compatibility of this powerful strategy provides a platform for synthesizing various polyacrylate‐based block copolymers comprising polyether, polycarbonate, polythiocarbonate, polyester, and polyurethane segments, respectively. [ABSTRACT FROM AUTHOR]

Block copolymers, comprising polyether and polyolefin segments, are an important and promising category of functional materials. However, the lack of efficient strategies for the construction of polyether‐b‐polyolefin block copolymers have hindered the development of these materials. Herein, we propose a simple and efficient method to obtain various block copolymers through the copolymerization of epoxides and acrylates via bimetallic synergistic catalysis. The copolymerization of epoxides and acrylates proceeds in a sequence‐controlled manner, where the epoxides‐involved homo‐ or copolymerization occurs first, followed by the homopolymerization of acrylates initiated by the alkoxide species from the propagating polymer chain, thus yielding copolymers with a block structure. Notably, the high monomer compatibility of this powerful strategy provides a platform for synthesizing various polyacrylate‐based block copolymers comprising polyether, polycarbonate, polythiocarbonate, polyester, and polyurethane segments, respectively. [ABSTRACT FROM AUTHOR]

Results of studying the catalytic properties of systems based on complexes with [Pd(Cp)(L)n]m[BF4]m (where Cp = η5-C5H5; n = 2, m = 1: L = tris(ortho-methoxyphenyl)phosphine, triphenylphosphine, tris(2-furyl)phosphine (TFP); n = 1, m = 1: L = 1,1'-bis(diphenylphosphino)ferrocene, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, 1,5-bis(diphenylphosphino)pentane; n = 1, m = 2 or 3: L = 1,6-bis(diphenylphosphino)hexane) in the addition homo- and copolymerization of norbornene (NB) and NB derivatives have been described. It has been found that these complexes can be activated with Lewis acids (BF3⋅OEt2 or AlCl3). The productivity of the [Pd(Cp)(PPh3)2][BF4]/BF3⋅OEt2 catalyst system in NB polymerization can achieve 188 800 molNB . The homopolymerization of 5-methoxycarbonylnorbornene and the copolymerization of NB with 5-methoxycarbonylnorbornene or 5-phenylnorbornene in the presence of BF3⋅OEt2 and [Pd(Cp)(L)2][BF4] (L = PPh3 or TFP) has been studied. A hypothesis for the formation of the catalyst via the intramolecular rearrangement of the η5-Cp ligand into the η1-Cp form upon interaction with a Lewis acid has been proposed. The structure of the [Pd(Cp)(TFP)2]BF4 complex (I) has been determined by X-ray diffraction (XRD) analysis. In the crystal structure of complex I, the coordination sphere of palladium is characterized by a slight distortion of the square planar geometry of the central atom, while the cyclopentadiyl moiety is in an eclipsed conformation. Based on XRD data, the steric hindrance of the TFP ligand has been determined (cone angle is 149°). [ABSTRACT FROM AUTHOR]

A simple and modular dialkylation of two electron‐rich pyridine derivatives, namely 4‐aminopyridine or 1,2,3,4‐tetrahydropyrido[3,4‐b]pyrazine, is achieved by aza‐Michael reactions with electron‐poor olefins (ethyl acrylate and acrylonitrile). Reducing the ester groups in the ethyl acrylate‐derived compounds yielded the corresponding hydroxyl‐containing derivatives. Subsequently, homopolymerization of phenyl glycidyl ether as well as an epoxy‐alcohol polyaddition are catalyzed using the introduced compounds. As a reference catalyst, 4‐dimethylaminopyridine is used. It is found that in all cases an irreversible termination of the polymerization at temperatures above 100 °C occurred. The decomposition is particularly rapid in the case of pyridine derivatives containing hydroxyl groups. In contrast, at a constant temperature of 100 °C, the latter compounds gave the fastest phenyl glycidyl ether homopolymerization and high conversions are found for all electron‐rich pyridine derivatives. However, testing the catalysts at high alcohol concentrations at temperatures higher than 100 °C resulted in similarly moderate conversions in all cases. [ABSTRACT FROM AUTHOR]

Through the graft polymerization of acrylic monomers onto starch, materials with interesting new properties can be synthesized. Fenton's chemistry, Fe2+/H2O2, is considered to be attractive for the initiation of graft polymerization with the monomer acrylic acid since it is cheap and reacts quickly at ambient conditions and should therefore be easy to scale up. However, the selectivity of the grafting versus the homopolymerization reaction poses a challenge with this monomer and this type of initiator. In the present review paper, we investigate why data from the literature on grafting systems with other monomers and initiation systems tend to show higher graft selectivity. A scheme is presented, based on reaction engineering principles, that supports an explanation for these observed differences. It is found that more selective activation of starch is a factor, but perhaps even more important is a low monomer-to-starch ratio at the starting sites of graft reactions. Since water is the most common solvent, monomers that are less water-soluble have an advantage in this respect. Based on the proposed scheme, methods to improve the graft selectivity with Fenton's initiator and acrylic acid are evaluated. Most promising appears to be a method of gradual monomer dosage. With gelatinized cassava starch in a batch reactor, both the grafting percentage (17 => 29%) and graft selectivity (18 => 31%) could be improved. This can be considered a principal breakthrough. Still, more research and development would be needed to refine the method and to implement the idea in a continuous reactor at a larger scale. [ABSTRACT FROM AUTHOR]

Radical thermally initiated homopolymerization of methacrylic monomers based on aurone has been studied. Photochemical properties of these methacrylic monomers by UV-visible spectroscopy were investigated. It is shown that the new compounds are capable to radical homopolymerization and photoinduced cis-trans isomerization. It was found that increasing the electron donation of the substituent accelerates the process of radical homopolymerization of monomers. It was found that increasing the electron acceptance of the substituent accelerates the process of cis-trans isomerization. The rate constants and half-transformation times of cis-trans photoisomerization were determined by the tangent of the slope of the dependence Ln(Dfss-D0)/(Dfss-Dt) on the irradiation time of the solutions. [ABSTRACT FROM AUTHOR]

The ring-opening polymerization (ROP) of epoxides, namely cyclohexene oxide (CHO), propylene oxide (PO), and tert-butyl glycidyl ether (tBuGE) catalyzed by Group 13 (Al, Ga, In) metal initiators is reported. These polymerization reactions were performed under solvent-free conditions and in the presence of chloroform (CHCl3) and toluene. InCl3 was the most efficient catalyst for the polymerization in the presence of CHCl3, and monomer loading up to 10,000 equivalents. It was observed that though the polymerization rate was slow in the presence of a solvent, the polymerization was much more controlled than in solvent-free conditions, producing exceptionally high molecular weights with narrow dispersities. The highest molecular weight of the polymer attained was 136.3 kg/mol, with CHO as the monomer. The order of reactivity for the epoxides was found to be CHO > tBuGE > PO. The polymerization reaction proceeds through an activated chain-end mechanism as established from the MALDI-TOF analysis of the polymer. These polymers were found to be atactic. [ABSTRACT FROM AUTHOR]

The aim of this work is to investigate the influence of the ethanol content of adducts on the catalytic behavior of related Ziegler–Natta (ZN) catalysts in propylene homo- and copolymerizations (with 1-hexene comonomer) in terms of activity, isotacticity, H2 response, and comonomer incorporation. For this purpose, three MgCl2.nEtOH adducts with n values of 0.7, 1.2, and 2.8 were synthesized and used in the synthesis of related ZN catalysts. The catalysts were thoroughly characterized using XRD, BET, SEM, EDX, N2 adsorption–desorption, and DFT techniques. Additionally, the microstructure of the synthesized (co)polymers was distinguished via DSC, SSA, and TREF techniques. Their activity was found to enhance with the adduct's ethanol content in both homo- and copolymerization experiments, and the increase was more pronounced in homopolymerization reactions in the absence of H2. Furthermore, the catalyst with the highest ethanol content provided a copolymer with a lower isotacticity index, a shorter meso sequence length, and a more uniform distribution of comonomer within the chains. These results were attributed to the higher total surface area and Ti content of the corresponding catalyst, as well as its lower average pore diameter, a larger proportion of large pores compared to the other two catalysts, and its spherical open bud morphology. It affirms the importance of catalyst/support ethanol-content control during the preparation process. Then, molecular simulation was employed to shed light on the iso-specificity of the polypropylene produced via synthesized catalysts. [ABSTRACT FROM AUTHOR]

The particle size distribution (PSD) in emulsion polymerization (EP) has been modeled in the past using either the pseudo bulk (PB) or the 0-1/0-1-2 approaches. There is some controversy on the proper type of model to be used to simulate the experimental PSDs, which are apparently broader than the theoretical ones. Additionally, the numerical technique employed to solve the model equations, involving hyperbolic partial differential equations (PDEs) with moving and possibly steep fronts, has to be precise and robust, which is not a trivial matter. A deterministic kinetic model for the PSD evolution of ab initio EP of vinyl monomers was developed to investigate these issues. The model considers three phases, micellar nucleation, and particles that can contain n ≥ 0 radicals. Finite volume (FV) and weighted-residual methods are used to solve the system of PDEs and compared; their limitations are also identified. The model was validated by comparing predictions with data of monomer conversion and PSD for the batch emulsion homopolymerization of styrene (Sty) and methyl methacrylate (MMA) using sodium dodecyl sulfate (SDS)/potassium persulfate (KPS) at 60 °C, as well as the copolymerization of Sty-MMA (50/50; mol/mol) at 50 and 60 °C. It is concluded that the PB model has a structural problem when attempting to adequately represent PSDs with steep fronts, so its use is discouraged. On the other hand, there is no generalized evidence of the need to add a stochastic term to enhance the PSD prediction of EP deterministic models. [ABSTRACT FROM AUTHOR]

A Monte Carlo model is employed to investigate the grafting of maleic anhydride onto polypropylene using a peroxide initiator. The study aimed to develop a comprehensive model that considered a very detailed kinetic mechanism, including chain transfer to polymer, homopolymerization as well as several copolymer reactions. The relative importance of these reactions is evaluated using a sensitivity analysis, which identified homopolymerization, β‐scission, chain grafting, and termination by disproportionation as the most influential reactions. The kinetic constants of these reactions are tuned to fit reported experimental data using the Surface Response Method. The model considers a pseudo‐homogeneous reaction medium and predicts average molecular weights, degree of grafting, molecular weight distribution, and grafting distribution. Furthermore, model simulations provided useful information about the impact of initial concentrations of reactants and reaction time on the molecular properties of the grafted polymer. [ABSTRACT FROM AUTHOR]

Zn plating on carbon steel (CS) was achieved applying current of 4 mA with galvanostatic technique in acidic medium. Zn particles had homogenous, smooth with spherical structure. It was shown that the Zn particles exhibited active behavior on CS substrate. Poly(aniline), poly(pyrrole), poly(N-methylpyrrole) and poly(o-anisidine) homopolymer films were obtained on CS/Zn electrode. Evaluation of anticorrosion performance of these homopolymer coatings in 3.5 % NaCl solution was investigated by using AC impedance spectroscopy (EIS) technique, anodic polarization and the Eocp-time curves. Homopolymer films exhibited significant physical barrier behavior on Zn plated carbon steel, in longer exposure time. [ABSTRACT FROM AUTHOR]

Enzymatic one-pot synthesis procedures in a one-step and two-step monomers addition were developed to obtain poly(glycerol adipate) macromers with methacrylate end-functional groups under the presence of 1 and 3 wt% of Candida antarctica lipase B (CALB). Glycerol, divinyl adipate, and vinyl methacrylate were enzymatically reacted (vinyl methacrylate was either present from the beginning in the monomers solution or slowly dropped after 6 h of reaction) in tetrahydrofuran (THF) at 40 °C over 48 h. Macromers with a methacrylate end groups fraction of ≈52% in a simple one-pot one-step procedure were obtained with molecular weights (Mn) of ≈7500–7900 g/mol. The obtained products under the one-pot one-step and two steps synthesis procedures carried out using 1 and 3 wt% of a CALB enzymatic catalyst were profusely characterized by NMR (1H and 13C), MALDI-TOF MS, and SEC. The methacrylate functional macromers obtained with the different procedures and 1 wt% of CALB were combined with an Irgacure® 369 initiator to undergo homopolymerization under UV irradiation for 10 and 30 min, in order to test their potential to obtain amorphous networks within minutes with similar properties to those typically obtained by complex acrylation/methacrylation procedures, which need multiple purification steps and harsh reagents such as acyl chlorides. To the best of our knowledge, this is the first time that it has been demonstrated that the obtention of methacrylate-functional predominantly linear macromers based on poly(glycerol adipate) is able to be UV crosslinked in a simple one-step procedure. [ABSTRACT FROM AUTHOR]

A series of novel Ni(II) and Pd(II) complexes bearing chiral bis(β-ketoamino) ligand were synthesized and characterized. The Ni(II) and Pd(II) complexes exhibited high activities for norbornene homopolymerization with only B(C6F5)3 as cocatalyst, for Ni(II) complex even up to 1.38 ×106 gpolymer/molNi·h. All the complexes had good thermal stability. Most importantly, the complexes also displayed high activities of 105 gpolymer/molmetal·h toward the copolymerization of norbornene and 5-norbornene-2-yl acetate with high molecular weights and tunable norbornene and 5-norbornene-2-yl acetate content. The copolymerization activity, molecular weight, and norbornene and 5-norbornene-2-yl acetate feed ratio of the Ni complex were higher than those of the Pd complex. [ABSTRACT FROM AUTHOR]

Through neodymium-mediated coordinative chain transfer copolymerizaiton (CCTcoP), polyisoprenes bearing dual hydroxylated mini-blocky chain-ends were prepared via a three-step strategy. Kinetic studies revealed that, the polymerization demonstrated typical features of CCTcoP across the whole polymerization process, i.e., quasi-living polymerization characteristic, tunable molecular weights, narrow molecular weight distributions, and atom economies. Comparing to previously reported CCTP homopolymerization systems, the presence of oxygen-containing IpOAl polar comonomer slowed down chain transfer rates obviously, rendering slightly higher molecular weights of the resultant PIps and smaller Np (number of polymer chains per Nd atom) values. Moreover, to mimic the structure of natural rubber, the hydroxyl end groups can be facilely modified into phosphonate, amide, and UPy, whose structures were further confirmed by NMR spectra. Incorporation these functionalities could greatly improve the hydrophilic properties of the polymers, as revealed from the significantly reduced static water contact angles. [ABSTRACT FROM AUTHOR]

Cyclic olefin copolymer is a type of high performance polyolefin material, which is prepared by using a single-site catalyst in solution polymerization. The common activator of this system is alkyl aluminoxane or organic boron/aluminum system. Among them, organic boron is mostly triphenylcarbenium tetrakis(pentafluorophenyl)borate or dimethylanilinium tetrakis(pentafluorophenyl)borate. In this study, ethylene and norbornene were copolymerized with metallocene catalyst activated with the combination of tris(pentafluorophenyl)boron and triisobutylaluminium. Compared with homopolymerization of ethylene, copolymerization shows high activity. The molecular weight of the polymer increased significantly with the increase of the insertion rate of norbornene. Fineman-Ross method was used to calculate the reactivity ratio, which showed that the reactivity ratio of norbornene was much lower than that of ethylene. The high copolymerization activity may indicate that, although norbornene has a lower coordination probability, its insertion rate is higher than ethylene. The copolymer with higher norbornene incorporation has a higher glass transition temperature, and the relationship between them is linear. [ABSTRACT FROM AUTHOR]

In situ heterogeneous olefin polymerization has attracted much attention for the synthesis of polyolefin composites. However, the complicated syntheses of specially designed catalysts or the detrimental effects of interactions between catalyst and solid supports pose great challenges. In this contribution, an outer‐shell self‐supporting strategy was designed to heterogenize nickel catalysts on different fillers via precipitation homopolymerization of ionic cluster type polar monomer. These catalysts demonstrated high activity, good product morphology control, and stable performances in ethylene polymerization and copolymerization. Moreover, various polyolefin composites with great mechanical and customized properties can be efficiently synthesized. [ABSTRACT FROM AUTHOR]

In situ heterogeneous olefin polymerization has attracted much attention for the synthesis of polyolefin composites. However, the complicated syntheses of specially designed catalysts or the detrimental effects of interactions between catalyst and solid supports pose great challenges. In this contribution, an outer‐shell self‐supporting strategy was designed to heterogenize nickel catalysts on different fillers via precipitation homopolymerization of ionic cluster type polar monomer. These catalysts demonstrated high activity, good product morphology control, and stable performances in ethylene polymerization and copolymerization. Moreover, various polyolefin composites with great mechanical and customized properties can be efficiently synthesized. [ABSTRACT FROM AUTHOR]

Titanium, zirconium, and hafnium complexes O[Me2Si(Dip)N]2MCl2 [Dip = 2,6‐iPr2C6H3; M = Ti (1), Zr (2), Hf (3)], O[Me2Si(tBu)N]2ZrCl2 (4), and O[iPr2Si(Dip)N]2ZrCl2 (5) supported by Si‐O‐Si bridged diamido ligands were synthesized. X‐ray diffraction analysis disclosed that complex 2 displays a distorted trigonal bipyramidal geometry. Complexes 1–5, upon the activation with sMAO, exhibited diverse catalytic performance for the polymerization of ethylene and copolymerization of ethylene with norbornene or 1‐octene. For ethylene homopolymerization, both complexes 1–2 are good catalysts giving polymer with high molecular weight and narrow polydispersities. Complex 2 catalyzed copolymerization of ethylene with 1‐octene exhibiting high catalytic activity but with norbornene showing moderate activity, affording corresponding high molecular weight copolymers with relatively high comonomer incorporations of 11% and 29%, respectively. [ABSTRACT FROM AUTHOR]

The OSSO-type diol ligand and the TiIV dichloride and bis-isopropoxide complexes with this ligand were synthesized. The structure of the latter complex was determined by single-crystal X-ray diffraction analysis. The catalytic activity of the systems based on the complexes (OSSO)TiCl2 and (OSSO)Ti(OPri)2, which were activated with mixtures of alkylaluminum chlorides (Et2AlCl, Et3Al2Cl3) and dibutylmagnesium, was studied in the polymerization of ethylene and its copolymerization with propylene. It was found that the homopolymerization affords ultra-high-molecular-weight polyethylene (UHMWPE) with a molecular weight up to 10.6·106, and the copolymerization gives copolymers containing up to 43 mol.% propylene units. [ABSTRACT FROM AUTHOR]

In this study, we designed a methacrylate molecule with an alkyl‐substituted trichloro salicylic acid pendant as a transformable bulky monomer to enable the synthesis of an alternating copolymer of methyl methacrylate (MMA) and n‐butyl acrylate (nBA). The adamantyl‐substituted methacrylate monomer (1‐Ad) showed very low homopolymerization propensity in radical polymerizations, but afforded the alternating copolymer with nBA via copolymerization. The 1‐Ad units in the resultant copolymer were quantitatively and selectively transformed into MMA via transesterification with methanol to yield the alternating copolymer of MMA and nBA. Its alternating sequence was clearly demonstrated by a structural analysis via 13C NMR spectroscopy as well as the low reactivity ratios for the 1‐Ad and nBA pair. Finally, we verified the superior self‐healing ability of the alternating copolymer compared to that of the corresponding 1 : 1 statistical copolymer. [ABSTRACT FROM AUTHOR]

In this study, we designed a methacrylate molecule with an alkyl‐substituted trichloro salicylic acid pendant as a transformable bulky monomer to enable the synthesis of an alternating copolymer of methyl methacrylate (MMA) and n‐butyl acrylate (nBA). The adamantyl‐substituted methacrylate monomer (1‐Ad) showed very low homopolymerization propensity in radical polymerizations, but afforded the alternating copolymer with nBA via copolymerization. The 1‐Ad units in the resultant copolymer were quantitatively and selectively transformed into MMA via transesterification with methanol to yield the alternating copolymer of MMA and nBA. Its alternating sequence was clearly demonstrated by a structural analysis via 13C NMR spectroscopy as well as the low reactivity ratios for the 1‐Ad and nBA pair. Finally, we verified the superior self‐healing ability of the alternating copolymer compared to that of the corresponding 1 : 1 statistical copolymer. [ABSTRACT FROM AUTHOR]

We studied the effect of side reactions on the reversibility of epoxy with thermoreversible Diels–Alder (DA) cycloadducts based on furan and maleimide chemistry. The most common side reaction is the maleimide homopolymerization which introduces irreversible crosslinking in the network adversely affecting the recyclability. The main challenge is that the temperatures at which maleimide homopolymerization can occur are approximately the same as the temperatures at which retro-DA (rDA) reactions depolymerize the networks. Here we conducted detailed studies on three different strategies to minimize the effect of the side reaction. First, we controlled the ratio of maleimide to furan to reduce the concentration of maleimide groups which diminishes the effects of the side reaction. Second, we applied a radical-reaction inhibitor. Inclusion of hydroquinone, a known free radical scavenger, is found to retard the onset of the side reaction both in the temperature sweep and isothermal measurements. Finally, we employed a new trismaleimide precursor that has a lower maleimide concentration and reduces the rate of the side reaction. Our results provide insights into how to minimize formation of irreversible crosslinking by side reactions in reversible DA materials using maleimides, which is important for their application as novel self-healing, recyclable, and 3D-printable materials. [ABSTRACT FROM AUTHOR]

The development of the modern society imposes a fast-growing demand for new advanced functional polymer materials. To this aim, one of the most plausible current methodologies is the end-group functionalization of existing conventional polymers. If the end functional group is able to polymerize, this method enables the synthesis of a molecularly complex, grafted architecture that opens the access to a wider range of material properties, as well as tailoring the special functions required for certain applications. In this context, the present paper reports on α-thienyl-ω-hydroxyl-end-groups functionalized oligo-(D,L-lactide) (Th-PDLLA), which was designed to combine the polymerizability and photophysical properties of thiophene with the biocompatibility and biodegradability of poly-(D,L-lactide). Th-PDLLA was synthesized using the path of "functional initiator" in the ring-opening polymerization (ROP) of (D,L)-lactide, assisted by stannous 2-ethyl hexanoate (Sn(oct)2). The results of NMR and FT-IR spectroscopic methods confirmed the Th-PDLLA's expected structure, while the oligomeric nature of Th-PDLLA, as resulting from the calculations based on 1H-NMR data, is supported by the findings from gel permeation chromatography (GPC) and by the results of the thermal analyses. The behavior of Th-PDLLA in different organic solvents, evaluated by UV–vis and fluorescence spectroscopy, but also by dynamic light scattering (DLS), suggested the presence of colloidal supramolecular structures, underlining the nature of the macromonomer Th-PDLLA as an "shape amphiphile". To test its functionality, the ability of Th-PDLLA to work as a building block for the synthesis of molecular composites was demonstrated by photoinduced oxidative homopolymerization in the presence of diphenyliodonium salt (DPI). The occurrence of a polymerization process, with the formation of a thiophene-conjugated oligomeric main chain grafted with oligomeric PDLLA, was proven, in addition to the visual changes, by the results of GPC, 1H-NMR, FT-IR, UV–vis and fluorescence measurements. [ABSTRACT FROM AUTHOR]

The ring-opening homopolymerization and copolymerization of ε-caprolactone (CL) and l-lactide (LA) in the presence of an aluminum complex with aminobisphenolate ligand MeN{CH2[(3-But)C6H3(2-O−)]}2Al−OMe (LAl−OMe) was modeled in terms of the density functional theory (DFT). The structures of transition states and intermediates were optimized for the initiation stage of the polymerization of CL and LA and for the first stage of the chain propagation reactions affording LAl−LA−LA−OMe, LAl−LA−CL−OMe, LAl−CL−LA−OMe, or LAl−CL−CL−OMe. The barriers to the rate-limiting stages were determined. A fundamental reactivity difference between CL and LA was established. It is associated with the formation of a stable chelate intermediate whose stability governs the distribution of monomeric units in the copolymer. The LAl−OMe complex exhibits a rare feature, viz., the polymerization of CL during the copolymerization in the presence of this initiator should proceed faster than the polymerization of LA, which leads to the preferential formation of the poly(CL-block-LA) block copolymer. [ABSTRACT FROM AUTHOR]

Epoxy (EP) was copolymerized with polyamic acid (PAA, precursor of polyimide (PI)) with termanil monomers of (1) 4,4′-Oxydianiline (ODA) and (2) pyromellitic dianhydride (PMDA) individually to form (PI-O-EP) and (PI-P-EP) copolymers. The FTIR spectrum of PI-O-EP copolymerization intermediates shows that some amide-EP linkages were formed at low temperature and were broken at higher temperature; in additoin, the released amide was available for subsequent imidization to form PI. The curing and imidization of the amide groups on PAA were determined by reaction temperature (kinetic vs. thermodynamic control). In PI-P-EP, the released amide group was very short-lived (fast imidization) and was not observed on FTIR spectra. Formation and breakage of the amide-EP linkages is the key step for EP homopolymerization and formation of the interpenetration network. PI contributed in improving thermal durability and mechanical strength without compromising EP's adhesion strength. Microphase separations were minimal at PI content less than 10 wt%. The copolymerization reaction in this study followed the "kinetic vs. thermodynamic control" principle. The copolymer has high potential for application in the field of higher-temperature anticorrosion. [ABSTRACT FROM AUTHOR]

The data on the synthesis of the new monomer benzamidmetacrylate are presented in the article. Its composition and structure were established by physical and chemical methods of research. The regularities of radical homopolymerization reactions in mass and in benzene solution were studied with the aim of creating a new biocidal polymeric material for medical preparations. It is shown that polymerization under these conditions proceeds through the vinyl bond, without an induction period, at a constant initial rate without the formation of by-products, a monotonic increase in conversion up to 92% with the formation of a soluble polymer is observed. The composition and structure of the obtained polymer were established by elemental and spectral analyses. It showed that the polymer was characterized by a low toxicity at a significant biocidal activity towards E.coli and St.Aureus and that this polymer can be used in various fields, in particular as a biocidal preparation, a carrier of dosage forms in medicine. In addition, this polymer also exhibites optical translucency and can be used in optics. [ABSTRACT FROM AUTHOR]

The radical homopolymerization of N‐tert‐butyl acrylamide (t‐BuAAm) and its copolymerization with methyl acrylate (MA) is studied in ethanol/water solutions over a range of initial monomer and initiator levels between 50 and 70 °C. While short‐chain branching for poly(t‐BuAAm) samples could not be detected by 13C NMR, the reduced rate of monomer conversion with lowered monomer content indicates the formation of mid‐chain radicals (MCR) by backbiting. Adding water as a cosolvent to ethanol significantly increases reaction rates, in agreement with recent pulsed‐laser studies that quantify the influence of solvent composition on homopropagation kinetics. However, the measured drifts in comonomer composition with conversion are well represented by a single pair of reactivity ratios (rMA = 1.12 ± 0.01, rt‐BuAAm = 0.71 ± 0.01) over the complete range of experimental conditions. A mechanistic model developed to describe t‐BuAAm homopolymerization is extended to capture the impact of reaction operating conditions (monomer content and composition, solvent composition, initiator content, and temperature) on the features of t‐BuAAm/MA copolymerization, thus providing a tool for product and process optimization. The model structure can be used to support the development of other acrylate/acrylamide systems as part of the continued efforts to utilize "green" solvents to reduce the environmental impacts of polymerization processes. [ABSTRACT FROM AUTHOR]

The reversible kinetics of copolymerization is solved analytically for the multistate mechanism proposed by Coleman and Fox [J. Chem. Phys. 38, 1065 (1963)] under low conversion conditions where the concentrations of monomeric species are chemostatted and stay constant in time. Although the rates of this mechanism only depend on the currently attached or detached monomer, the growing macromolecular chain forms a non-Markovian sequence that is characterized by matrices associated with every monomeric unit composing the sequence. These matrices are obtained by solving the kinetic equations, and they determine the growth velocity of the copolymers, the statistical properties of its possible sequences, as well as the thermodynamics of the copolymerization process. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are used to study the diffusion of polymer-grafted nanoparticles (PGNPs) in polymer. The diffusivity of PGNPs in the homopolymer matrix is investigated as a function of graft length and grafting density, and it is compared to that of bare nanoparticles with comparable effective size. Our results indicate that, in addition to the increase in the effective size of PGNPs due to grafting, the interpenetration of matrix polymers into the grafted layer also plays an important role in the mobility of PGNPs. In systems consisting of both PGNPs and bare particles, the spatial arrangement of the bare particles was found to be having a significant influence on the mobility of PGNPs. At low graft length and high grafting density, the matrix chains dewets the grafted layer, due to autophobic dewetting, creating a sharper interface between the matrix and the grafted layer. The bare particles then migrate to the interface creating a barrier around the PGNPs that hinders the matrix-graft interpenetration and results in the higher mobility of PGNPs. Our results emphasize the importance of polymer-particle interface on the dynamic properties of polymer nanocomposites. [ABSTRACT FROM AUTHOR]

In this work, we investigated whether a series of nanopores connected by channels can be used to separate polymer mixtures by molecular size. We conducted multiscale coarse-grained simulations of semiflexible polymers driven through such a device. Polymers were modelled as chains of beads near the nanopores and as single particles in the bulk of the channels. Since polymers rarely escape back into the bulk of the channels after coming sufficiently close to the nanopores, the more computationally expensive simulations near the pores were decoupled from those in the bulk. The distribution of polymer positions after many translocations was deduced mathematically from simulations across a single nanopore-channel pair, under the reasonable assumption of identical and independent dynamics in each channel and each nanopore. Our results reveal rich polymer dynamics in the nanopore-channel device and suggest that it can indeed produce polymer separation. As expected, the mean time to translocate across a single nanopore increases with the chain length. Conversely, the mean time to cross the channels from one nanopore to the next decreases with the chain length, as smaller chains explore more of the channel volume between translocations. As such, the time between translocations is a function of the length and width of the channels. Depending on the channel dimensions, polymers are sorted by increasing length, decreasing length, or non-monotonically by length such that polymers of an intermediate size emerge first. [ABSTRACT FROM AUTHOR]

Transition metal‐catalyzed copolymerization of CO and ethylene has a strong inherent propensity to produce the strictly alternating copolymer. In this work, nickel catalysts capable of both homopolymerization of ethylene and alternating copolymerization of CO and ethylene are developed to explore the possibility of non‐alternating copolymerization of CO and ethylene under the assumption that comonomer incorporation in the polymer chain can be adjusted by the concentrations of the comonomers. Both polyketones with slightly more than 50 % ethylene and "polyethylenes" with a small amount of CO incorporation are obtained but only under carefully controlled conditions and in low yields. [ABSTRACT FROM AUTHOR]

Ethylene polymerization and ethylene/1-hexene copolymerization over the titanium–magnesium catalytic system in the presence of chlorocyclohexane (CHC) and hexachloro-p-xylene (HCPX) has been studied. Modification of TMC with chlorocyclohexane and hexachloro-p-xylene increased catalyst activity severalfold for both ethylene polymerization and ethylene/1-hexene copolymerization. The key kinetic regularities of ethylene homopolymerization and ethylene/1-hexene copolymerization in the presence of CHC and HCPX were determined, and the copolymerization constants were measured. Molecular characteristics and the copolymer composition were determined for the synthesized samples of ethylene homopolymers and ethylene/hexene copolymers. Modification of the titanium–magnesium catalyst with chlorinated organic compounds reduced 1-hexene content in the copolymer; polymerization was sensitive to 1-hexene as a regulator of polymer molecular weight. The potential mode of action of chlorinated organic modifiers on catalytic properties of titanium–magnesium catalyst is discussed. [ABSTRACT FROM AUTHOR]

The zinc complex Zn(C6F5)2(toluene) (1) behaves as a very active and selective catalyst in cyclohexene oxide (CHO) polymerization to produce poly(cyclohexene oxide) (PCHO) by the trans-ring-opening of CHO with remarkable TOF values at room temperature. The ring-opening copolymerization (ROCOP) of CO2 with CHO catalysed by 1 yields poly(cyclohexene carbonate) (PCHC) when using benzyl alcohol (BnOH) as an initiator at 120 °C. The 1H NMR monitoring of the in situ reaction of 1 with BnOH highlighted the formation of the dinuclear species [(C6F5)2Zn2(BnO)2 (2) that was isolated and found an active catalyst in the ROCOP of CO2 with CHO in the absence of initiators. Interestingly, PCHCs by 2 in solventless conditions show polydispersity index (Mw/Mn) values close to 2, corresponding to those expected for a single-site catalyst; on the contrary, a broader polydispersity index of the polymer products was found in toluene solution, suggesting the formation of new zinc catalysts during the polymerization reaction. [ABSTRACT FROM AUTHOR]

Four examples of para-nitro substituted 2-(arylimino)pyridine-nickel(II) bromide complexes of general formula, [2-{(2,6-R-4-NO2C6H2)N=CMe}C5H4N]NiBr2, but differentiable by the steric/electronic properties displayed by the ortho-groups [R = i-Pr (Ni1), Et (Ni2), CHPh2 (Ni3), CH(4-FPh)2 (Ni4)], have been prepared in good yield. For comparative purposes, the meta-nitro complex, [2-{(2,6-i-Pr2-3-NO2-4-(4-FPh)2C6H)N=CMe}C5H4N]NiBr2 (Ni5), has also been synthesized. The molecular structures of mononuclear Ni3·xH2O (x = 2, 3) and bromide-bridged dinuclear Ni4 and Ni5 are disclosed. Upon activation with either ethylaluminum dichloride (EtAlCl2) or modified methylaluminoxane (MMAO), all precatalysts displayed good catalytic performance at operating temperatures between 30 °C and 60 °C with higher activities generally seen using EtAlCl2 [up to 4.7 × 106 g PE (mol of Ni)−1 h−1]: Ni2 ~ Ni5 > Ni1 ~ Ni4 > Ni3. In terms of the resultant polyethylene (PE), Ni4/EtAlCl2 formed the highest molecular weight of the series (Mw up to 1.4 × 105 g mol−1) with dispersities (Mw/Mn) ranging from narrow to broad (Mw/Mn range: 2.2–24.4). Moreover, the melting temperatures (Tm) of the polymers generated via EtAlCl2 activation fell in a narrow range, 117.8–126.0 °C, which resembles that seen for industrial-grade linear-low density polyethylene (LLDPE). Indeed, their 13C NMR spectra revealed significant amounts of uniformly distributed long-chain branches (LCBs), while internal vinylene groups constituted the major type of chain unsaturation [vinylene:vinyl = 5.3:1 (EtAlCl2) and 9.9:1 (MMAO)]. [ABSTRACT FROM AUTHOR]

Four supported α-diimine nickel(II) catalysts covalently linked to silica via hydroxyl functionality on α-diimine acenaphthequinone-backbone were prepared and used in slurry polymerizations of ethylene to produce branched polyethylenes. The catalytic activities of these still reached 106 g/molNi·h at 70 °C. The life of the supported catalyst is prolonged, as can be seen from the kinetic profile. The molecular weight of the polyethylene obtained by the 955 silica gel supported catalyst was higher than that obtained by the 2408D silica gel supported catalyst. The melting points of polyethylene obtained by the supported catalysts S-C1-a/b are all above 110 °C. Compared with the homogeneous catalyst, the branching numbers of the polyethylenes obtained by the supported catalysts S-C1-a/b is significantly lower. The polyethylenes obtained by supported catalyst S-C1-a/b at 30–50 °C are free-flowing particles, which is obviously better than the rubber-like cluster polymer obtained from homogeneous catalyst. [ABSTRACT FROM AUTHOR]

A simple mathematical model of the transport of monomer from the monomer droplets to the polymerizing polymer particles during batch emulsion homopolymerization has been developed and published previously. A Damkohler number for monomer transport in emulsion polymerization is proposed as the ratio of the maximum rate of polymerization divided by the maximum rate of monomer transport out of the monomer droplets. This Damkohler number is calculated from literature values for a number of common monomers. Following standard practice for the use of such a Damkohler number in other reaction‐with‐transport systems, monomers with a Damkohler number above 0.1 are considered to be transport limited. In a third paper the analysis is extended to batch binary copolymerization. Here the analysis is extended to the more industrially relevant cases of batch terpolymerization, starved‐feed copolymerization, and the combination of the two (starved‐feed terpolymerization). [ABSTRACT FROM AUTHOR]

Among nitrogen-containing cationic electrolytes, diallyl quaternary ammonium salt is a typical monomer with the highest positive charge density, which has attracted the most attention, especially in the research on homopolymers and copolymers of dimethyl diallyl ammonium chloride (DMDAAC), which occupy a very unique and important position. In order to improve the lipophilicity of substituted diallyl ammonium chloride monomers under the premise of high cationic charge density, the simplest, most direct, and most efficient structure design strategy was selected in this paper. Only one of the substituents on DMDAAC quaternary ammonium nitrogen was modified by alkyl; the substituents were propyl and amyl groups, and their corresponding monomers were methyl propyl diallyl ammonium chloride (MPDAAC) and methyl amyl diallyl ammonium chloride (MADAAC), respectively. The effect of substituent structure on the homopolymerization activity of methyl alkyl diallyl ammonium chloride was illustrated by quantum chemical calculation and homopolymerization rate determination experiments via ammonium persulfate (APS) as the initiator system. The results of quantum chemistry simulation showed that, with the finite increase in substituted alkyl chain length, the numerical values of the bond length and the charge distribution of methyl alkyl diallyl ammonium chloride monomer changed little, with the activation energy of the reactions in the following order: DMDAAC < MPDAAC < MADAAC. The polymerization activities measured by the dilatometer method were in the order DMDAAC > MPDAAC > MADAAC. The activation energies Ea of homopolymerization were 96.70 kJ/mol, 97.25 kJ/mol, and 100.23 kJ/mol, and the rate equation of homopolymerization of each monomer was obtained. After analyzing and comparing these results, it could be easily found that the electronic effect of substituent was not obvious, whereas the effect of the steric hindrance was dominant. The above studies have laid a good foundation for an understanding of the polymerization activity of methyl alkyl diallyl ammonium chloride monomers and the possibility of preparation and application of these polymers with high molecular weight. [ABSTRACT FROM AUTHOR]

(R)‐Limonene, a renewable terpene, and its epoxidized derivatives, i. e. limonene epoxides, have prompted growing attention over the last decade as building blocks for the synthesis of biobased monomers and polymers. With the goal of replacing petroleum‐based polymers several polymerization techniques have been applied on limonene oxide and limonene dioxide monomers. This paper aims to contribute to the literature by presenting a review dedicated to limonene oxide and dioxide as raw monomers of renewable origin for the development of biobased polymers. The polymerization techniques described are namely the homopolymerization, the copolymerization with carbon dioxide and anhydrides, and the copolymerization of limonene epoxide‐based monomers. Limonene oxide polymerizations will be investigated first, followed by limonene dioxide polymerizations. [ABSTRACT FROM AUTHOR]

Field-theoretic simulations (FTSs) are performed on ternary blends of A- and B-type homopolymers of polymerization Nh and symmetric AB diblock copolymers of polymerization Nc. Unlike previous studies, our FTSs are conducted in three-dimensional space, with the help of two new semi-grand canonical ensembles. Motivated by the first experiment to discover bicontinuous microemulsion (BμE) in the polyethylene-polyethylene propylene system, we consider molecules of high molecular weight with size ratios of α ≡ Nh/Nc = 0.1, 0.2, and 0.4. Our focus is on the A + B coexistence between the two homopolymer-rich phases in the low-copolymer region of the phase diagram. The Scott line, at which the A + B phases mix to form a disordered melt with increasing temperature (or decreasing χ), is accurately determined using finite-size scaling techniques. We also examine how the copolymer affects the interface between the A + B phases, reducing the interfacial tension toward zero. Although comparisons with self-consistent field theory (SCFT) illustrate that fluctuation effects are relatively small, fluctuations do nevertheless produce the observed BμE that is absent in the SCFT phase diagram. Furthermore, we find evidence of three-phase A + B + BμE coexistence, which may have been missed in the original as well as subsequent experiments. [ABSTRACT FROM AUTHOR]

Inspired by the protein folding and DNA packing, we have systematically studied the thermodynamic and kinetic behaviors of single semiflexible homopolymers by Langevin dynamics simulations. In line with experiments, a rich variety of folding products, such as rod-like bundles, hairpins, toroids, and a mixture of them, are observed in the complete diagram of states. Moreover, knotted structures with a significant population are found in a certain range of bending stiffness in thermal equilibrium. As the solvent quality becomes poorer, the population of the intermediate occurring in the folding process increases, which leads to a severe chevron rollover for the folding arm. However, the population of the intermediates in the unfolding process is very low, insufficient to induce unfolding arm rollover. The total types of folding pathways from the coil state to the toroidal state for a semiflexible polymer chain remain unchanged by varying the solvent quality or temperature, whereas the kinetic partitioning into different folding events can be tuned significantly. In the process of knotting, three types of mechanisms, namely, plugging, slipknotting, and sliding, are discovered. Along the folding evolution, a semiflexible homopolymer chain can knot at any stage of folding upon leaving the extended coil state, and the probability to find a knot increases with chain compactness. In addition, we find rich types of knotted topologies during the folding of a semiflexible homopolymer chain. This study should be helpful in gaining insight into the general principles of biopolymer folding. [ABSTRACT FROM AUTHOR]

Novel thermo-responsive shape-memory vanillin-based photopolymers have been developed for microtransfer molding. Different mixtures of vanillin dimethacrylate with tridecyl methacrylate and 1,3-benzenedithiol have been tested as photocurable resins. The combination of the different reaction mechanisms, thiol-acrylate photopolymerization, and acrylate homopolymerization, that were tuned by changing the ratio of monomers, resulted in a wide range of the thermal and mechanical properties of the photopolymers obtained. All polymers demonstrated great shape-memory properties and were able to return to their primary shape after the temperature programming and maintain their temporary shape. The selected compositions weretested by the microtransfer molding technique and showed promising results. The developed thermo-responsive shape-memory bio-based photopolymers have great potential for forming microtransfered structures and devices applicable on non-flat surfaces. [ABSTRACT FROM AUTHOR]

One‐step synthesis of well‐defined block copolymer is of great fundamental and practical values. Here, an aromatic‐aliphatic block copolyester is one‐step synthesized from the mixture of phthalic anhydride (PA), cyclohexene oxide (CHO), and δ‐valerolactone (δ‐VL) at room temperature in the presence of a metal‐free Lewis pair catalyst consisting of triethylborane and excess phosphazene base. Alcohol‐initiated ring‐opening alternating copolymerization of PA and CHO occurs first and selectively because of the overwhelmingly higher activity of PA than CHO and δ‐VL toward the reaction with base‐activated hydroxy species. Only after full conversion of PA is reached can ring‐opening polymerization of δ‐VL occur from the terminus of the aromatic polyester so that a well‐defined (AB)nCm type block copolyester is formed. The two polymerizations are both highly chemoselective without homopolymerization of CHO or extensive transesterification reactions. Owing to the sequence‐selective and living characteristics of the terpolymerization, hepta‐ and undecablock copolyesters with controlled molar mass and low dispersity are obtained through addition of the three‐component monomer mixture in batches. Applicability of the method to propylene oxide and ε‐caprolactone is also examined. [ABSTRACT FROM AUTHOR]

We present results for the nonequilibrium dynamics of collapse for a model flexible homopolymer on simple cubic lattices with fixed and fluctuating bonds between the monomers. Results from our Monte Carlo simulations showthat, phenomenologically, the sequence of events observed during the collapse are independent of the bond criterion. While the growth of the clusters (of monomers) at different temperatures exhibits a non-universal power-law behavior when the bonds are fixed, the introduction of fluctuations in the bonds by considering the existence of diagonal bonds produces a temperature independent growth, which can be described by a universal nonequilibrium finite-size scaling function with a non-universal metric factor. We also examine the related aging phenomenon, probed by a suitable two-time density-density autocorrelation function showing a simple power-law scaling with respect to the growing cluster size. Unlike the cluster-growth exponent λC, the nonequilibrium autocorrelation exponent αc governing the aging during the collapse, however, is independent of the bond type and strictly follows the bounds proposed by Majumder and Janke [Phys. Rev. E 93, 032506 (2016)] at all temperatures. [ABSTRACT FROM AUTHOR]

The paper reports studies of the effects of ester side-group size and structure on chain transfer to polymer (CTP) and mol% branches (%br) in the final polymers from monomer-starved semi-batch emulsion homopolymerizations of a series of alkyl acrylates with different numbers of ester OR side-group carbon atoms (NsgC) in the range 1–10. Although the high instantaneous conversions and high gel contents in the final polymers show that intermolecular CTP is significant, the kinetics have been analysed principally in terms of intramolecular CTP (intraCTP) because this is expected to be numerically the dominant CTP process. For linear OR side groups, there is a small, continuous increase in %br (from ~ 3.4 to ~ 5.0 mol%) as NsgC increases from 1 to 8, which arises predominantly from the acrylate molar mass (Macrylate) reducing the molar monomer concentration and from the small increase in rate coefficient for propagation (kp) as NsgC increases; no discernible effects of NsgC on the rate coefficient for intraCTP ( k trP intra ) are evident. For isomeric butyl acrylates, there is no measurable effect of isomer structure on %br (4.3–4.4 mol%), indicating that butyl groups are too small for changes in side-group bulkiness to influence k trP intra and kp. A similar observation was made for n-hexyl acrylate (nHA) and 2-ethylbutyl acrylate (%br 4.7–4.8 mol%). However, cyclohexyl acrylate (cHA) gives a much higher %br (~ 7.2 mol%), which has been assigned to steric effects increasing k trP intra because kp values for nHA and cHA are very similar. For OR side-groups with NsgC of 8 and10, there is a strong effect of side-group non-linearity (2-ethylhexyl, iso-octyl and iso-decyl) increasing %br, with polymers from n-alkyl acrylates having much lower %br (~ 4.5–5.0 mol%) than those from the equivalent non-linear acrylates (~ 6.7–7.1 mol%); since the kp values are expected to be similar for these acrylates, it is evident that the much bulkier non-linear OR groups cause a significant increase in k trP intra compared to the linear equivalents. Tentative hypotheses for these steric effects have been postulated. Studies of the effect of temperature (0–80 °C) on CTP and %br for methyl acrylate solution homopolymerization (in which intraCTP should be completely dominant) show the expected reduction in %br as temperature reduces, such that CTP is negligible at 0 °C; Arrhenius analysis gives an activation energy of 40.7 kJ mol−1 for intraCTP, which is within the range of values reported for n-butyl acrylate. [ABSTRACT FROM AUTHOR]

A family of half-titanocene complexes bearing π,π-stacked aryloxide ligands and their catalytic performances towards ethylene homo-/co- polymerizations were disclosed herein. All the complexes were well characterized, and the intermolecular π,π-stacking interactions could be clearly identified from single crystal X-ray analysis, in which a stronger interaction could be reflected for aryloxides bearing bigger π-systems, e.g., pyrenoxide. Due to the formation of such interactions, these complexes were able to highly catalyze the ethylene homopolymerizations and copolymerization with 1-hexene comonomer, even without any additiveson the aryloxide group, which showed striking contrast to other half-titanocene analogues, implying the positive influence of π,π-stacking interaction in enhancing the catalytic performances of the corresponding catalysts. Moreover, it was found that addition of external pyrene molecules was capable of boosting the catalytic efficiency significantly, due to the formation of a stronger π,π-stacking interaction between the complexes and pyrene molecules. [ABSTRACT FROM AUTHOR]

Since cerium(IV) ammonium nitrate (CAN) could oxidize amidyl N–H moieties into nitrogen-centered radicals under proper conditions to initiate radical polymerization, CAN-acrylamide (AAm) redox-initiated radical homo/co-polymerization in a conventional or controlled manner was exploited with AAm as an intrinsically reducing inimer. CAN oxidized AAm to initiate conventional radical homopolymerization at 50–60 °C, and viscosity-average molecular weight (MW) of polyacrylamide (PAAm) steadily increased with conversion because of the oxidation of amidyl N–H moieties of in-chain -AAm- units, but MW was in a range from 104 to 105. CAN-AAm redox-initiated radical co-polymerization of N,N-dimethylacrylamide (DMAAm) proceeded readily under optimized conditions and formed PAAm-co-PDMAAm with MW in a range from 105 to 106, and increasing simultaneously with conversion. CAN-AAm redox-initiated controlled radical homopolymerization was performed with FeCl3 complexes as the deactivator, and the polymerization proceeded in a mechanism of reverse atom transfer radical polymerization (ATRP) and MW of PAAm increased in proportion to conversion. The PAAm chains contained a C–Cl terminal, which was confirmed by block co-polymerization with DMAAm via standard ATRP with PAAm as the macro-initiator. [ABSTRACT FROM AUTHOR]