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This article describes the synthesis of ethylene‐propylene‐diene terpolymers grafted with poly(methyl acrylate) (PMA) by reverse atom transfer radical polymerization. The PMA graft molecular weights and densities are controlled by varying the concentration and conversion of methyl acrylate, as well as the concentration of initiator. The grafted copolymers are characterized by Fourier‐transform infrared spectroscopy, proton NMR, and gel permeation chromatography. Copolymers with graft molecular weights varying from 12 to 179 kDa and grafting densities from 11% to 53% are made following this procedure. [ABSTRACT FROM AUTHOR]

Me6TREN (tris[2‐(dimethylamino)ethyl]amine) is commonly used in Cu(0)‐mediated polymerization of acrylates due to its ability to promote high reaction rates while maintaining excellent control of chain growth. However, its cost presents a significant barrier to commercialization. Thus, the use of PMDETA (N,N,Nʹ,Nʹʹ,Nʹʹ‐pentamethyldiethylenetriamine), a ligand that is significantly less expensive than Me6TREN but is known to reduce the polymerization rate as well as control, is explored. The continuous production of low molecular weight (MW) poly(methyl acrylate) using PMDETA ligand in a copper tubular reactor is demonstrated, with conversions >70% achieved with a residence time of 32 min at 70 °C. The resulting macroinitiator solution can be stored and chain extended with methyl acrylate (MA) to high conversion in a semibatch reactor using either PMDETA or Me6TREN as additional ligand, increasing the versatility of a newly developed process to efficiently produce block copolymers using either ligand, or a combination of the two. First results suggest that the two‐step process can also be used to chain extend the macroinitiator with methacrylates, thus extending the range of materials that can be produced. [ABSTRACT FROM AUTHOR]

Postmodification methods are effective tools in preparing functional polymers, and novel end‐group reactions have attracted much attention from researchers for postmodification applications. Here, a new high‐efficiency postmodification method is proposed, which can change bromine‐containing polymers to functional polymers in one step. Phenol, 1‐hydroxynaphthalene, and 4‐(2‐phenyldiazenyl)‐phenol (AzoOH) are successfully grafted onto the polymeric branch chain of bromine‐containing polymers, i.e., homopolymer, bromoethyl methyl acrylate, (pBMEA) and amphiphilic block copolymer p(BMEA)‐b‐p(mPEG), with a high grafting rate that is near 100%. Also, the micelles of the postmodified amphiphilic block copolymer p(BMEA‐Azo)‐b‐p(mPEG) are broken up under ultraviolet irradiation. The proposed method can be used as a platform to prepare a variety of stimuli‐responsive polymeric nanoparticles. [ABSTRACT FROM AUTHOR]

Regioselective addition of nonsymmetrical monomers in radical polymerization is a basic issue for control of the reaction kinetics and structure of the resulting products. In reversible addition‐fragmentation chain transfer (RAFT) polymerization, head addition generates primary alkyl adducts when trapped by RAFT agents. Due to the low leaving ability of primary alkyl radicals, this kind of adduct in RAFT polymerization will become nonactive macro‐RAFT agents, that is, dead dormant species (DDS). Based on the previously‐developed equation for the correlation of DDS content (α) with head‐addition incidence (ρ1) in RAFT polymerization and the quantitative determination method of DDS content by coupling a block‐polymerization derivatization with gradient polymer elution chromatography analysis, the ρ1 values of methyl acrylate (MA) at different temperatures are determined with benzyl N‐carbazolecarbodithioate (BCBD) as RAFT agent and 2‐methyloxyethyl acrylate as the second monomer for block‐polymerization derivatization. The results show that the ρ1 values of MA at 60, 70, 80, and 90 °C are 2.04 × 10−3, 2.37 × 10−3, 2.72 × 10−3, and 3.28 × 10−3, respectively, and the activation energy for ρ1 is 15.8 kJ mol−1. The DDS in BCBD‐mediated RAFT polymerization of MA is separated by column chromatography and characterized by 1H‐NMR and MALDI‐TOF MS. [ABSTRACT FROM AUTHOR]

Monobrominated versions of poly(methyl methacrylate) (PMMABr) and poly(methyl acrylate) (PMABr) are prepared by atom transfer radical polymerization and subjected to a variety of chain end‐coupling reactions, with the goal of achieving high extents of coupling with minimal metal content. By using atom transfer radical coupling (ATRC) with radical trap assistance in conjunction with activators generated by electron transfer, high extents of coupling (Xc) could be achieved for both polymer classes without requiring copper(I) as an initial reactant, and replacing elemental copper with environmentally benign reducing agents (Xc > 0.85). Specifically, the highest extents of coupling are observed with ascorbic acid as the reducing agent along with copper(II) bromide as the pre‐catalyst. Overall, similar extents of coupling are observed while using ≈1% of the total metal of a traditional ATRC reaction for PMABr and ≈3% for PMMABr. [ABSTRACT FROM AUTHOR]

Abstract: Temperature‐sensitive amphiphilic block copolymers of 2,2‐dimethyl‐1,3‐dioxolan‐4‐yl‐methyl acrylate (solketal acrylate, SKA) and N‐isopropyl acrylamide (NIPAAm) have been prepared via reversible addition‐fragmentation chain transfer radical polymerization (RAFT). A kinetics study of SKA polymerization is performed in order to find a compatible RAFT chain transfer agents (CTA) and versatile polymerization conditions for the synthesis of well‐defined poly(2,2‐dimethyl‐1,3‐dioxolan‐4‐yl‐methyl acrylate) (PSKA). Depending on the RAFT‐CTA and the reaction time, PSKA with molar masses up to 5700 g mol−1 and dispersity values as low as 1.1 could be prepared. Additionally, the end group distribution of PSKA is investigated via electrospray ionization‐ion mobility separation–mass spectrometry. The chain extensions of the homopolymers for the second block of NIPAAm are analyzed with size‐exclusion chromatography. Amphiphilic block copolymers are obtained after hydrolysis of hydrophobic PSKA block to target hydrophilic poly(2,3‐dihydroxypropyl acrylate) block. [ABSTRACT FROM AUTHOR]

Abstract: A one‐pot, two‐step method is applied to the controlled synthesis of polyacrylate‐b‐(polycaprolactone)2 three‐arm AB2‐type star block polymers. First, ring‐opening polymerization (ROP) of ε‐caprolactone is carried out in toluene using either stannous octoate (Sn(Oct)2) or diphenyl phosphate (DPP) as catalyst, and a multifunctional initiator featuring one bromoester and two alcohol groups. Then, single‐electron transfer living radical polymerization (SET‐LRP) of methyl acrylate and isobornyl acrylate is conducted in the same reaction vessel after sequential addition of its typical reactants, apart from the (PCL)2‐Br macroinitiator generated in the first step, in either toluene/toluene + phenol or toluene/dimethyl sulfoxide solvent systems. DPP (the ROP catalyst) from the first step is found to take part in an acid–base reaction with tris[2‐(dimethylamino)ethyl]amine (the SET‐LRP N‐ligand) in the second part, but stoichiometry could be adjusted to avoid interference and keep the controlled nature of the polymerizations. Interestingly, the electrochemically active Sn(Oct)2 ROP catalyst does not interfere with the SET‐LRP process. Well‐defined poly(methyl acrylate)‐b‐(polycaprolactone)2 and poly(isobornyl acrylate)‐b‐(polycaprolactone)2 are thus synthesized through a simple and cost‐effective experimental procedure. The technique also applies to the synthesis of linear block copolymers. [ABSTRACT FROM AUTHOR]

Reversible addition-fragmentation chain transfer (RAFT) copolymerization of styrene (St) and 4-(diphenylphosphino)styrene (DPPS) is explored to establish the statistical distribution of the phosphine-functional monomer within the copolymer. RAFT copolymerization of St and DPPS at a variety of feed ratios provides phosphine-functional copolymers of low dispersity at moderate monomer conversion ( Ð < 1.2 at conv. >60%). In all cases, the fraction of DPPS in the resulting polymers is greater than that in the monomer feed. Estimation of copolymerization reactivity ratios indicates DPPS has a strong tendency to homopolymerize while St preferentially copolymerizes with DPPS ( rDPPS = 4.4; rSt = 0.31). The utility of the copolymers as macro-RAFT agents in block copolymer synthesis is demonstrated via chain extension with hydrophilic acrylamide ( N, N-dimethylacrylamide (DMAm)) and acrylate (poly(ethylene glycol) methyl ether acrylate (mPEGA), and di(ethylene glycol) ethyl ether acrylate (EDEGA)) monomers. Finally, access to polymers containing phosphine oxide and phosphonium salt functionalities is shown through postpolymerization modification of the phosphine-containing copolymers. [ABSTRACT FROM AUTHOR]

The polymerization of methyl acrylate and styrene in the presence of 1,1-diphenylethylene (DPE) is investigated to monitor the impact of different monomers on the structure of DPEcontaining polymers. Poly(methyl acrylate) (PMA) and polystyrene (PSt) with low molecular weight are synthesized and characterized. According to the results of the 1H nuclear magnetic resonance (1H-NMR) spectroscopy, DPE is incorporated into PMA and PSt polymer chains as diphenyl-substituted structure. The resulting PMA polymers containing only one DPE unit show good agreement with the mass spectrometry results obtained by electrospray-ionization quadrupolar time-of-fl ight mass spectrometry. The gel permeation chromatography results of PSt polymers are consistent with the molecular weight obtained by 1H-NMR, indicating that each PSt polymer chain has only one DPE molecule. [ABSTRACT FROM AUTHOR]

The solution properties of the multiresponsive polymer P1 (poly(2-((3-(1-(2-(dimethylamino)ethyl)-1H-1,2,3-triazol-4-yl)propanoyl)oxy)ethyl methacrylate) are studied by small angle neutron scattering (SANS) and dynamic light scattering (DLS). The P1 solution exhibits a phase transition above certain temperatures and cloud points following dissolution through the incubation at room temperature. SANS and DLS studies show that P1 forms clusters via hydrophobic interactions, which are weakened by continued incubation. The temperature dependent cluster formation is explained by hydrophobic adsorption and shrinking behavior as a function of hydrodynamic radius, correlation lengths, and Porod exponents. The weak clustering and solution property are discussed on the basis of Flory theory. Taken together, the results here indicate that time-dependent dissolution of P1 leads to a weakly hydrophobic structure. [ABSTRACT FROM AUTHOR]

Poly( tert-butoxycarbonylaminomethylacrylate) (P tBAMA), a derivative of polydehydroalanine (PDha), is synthesized using free radical polymerization (FRP) and nitroxide mediated polymerization (NMP). Due to the presence of orthogonal protective groups, the resulting polymers can be selectively deprotected to yield either a polyanion (poly( tert-butoxycarbonylaminoacrylic acid), P tBAA) or a polycation (poly(aminomethylacrylate), PAMA). Deprotection of both the amino- and the carboxyl-functionality in a sequential manner leads to the potential polyzwitterion polydehydroalanine (PDha). The pH-dependent solution behavior of P tBAA, PAMA, and PDha are examined in aqueous solution by potentiometric and turbidimetric titrations as well as ζ-potential measurements. [ABSTRACT FROM AUTHOR]

Isotactic poly(methyl methacrylate) and syndiotactic poly(methyl methacrylate) form a stereocomplex using an inkjet system. As compared with conventional methods such as simply mixing solutions or dipping substrates with a layer-by-layer (LbL) approach, a much smaller amount of polymer chains (9.0 × 107) can theoretically associate with each other, and the process is quicker. Glass and polystyrene substrates are compared as substrates, suggesting different morphologies due to the solvent interactions during the rapid evaporation. The stereocomplex structure is confirmed by infrared spectroscopy and X-ray diffraction. [ABSTRACT FROM AUTHOR]

Monobrominated versions of poly(pentafluorostyrene) (PPFSBr), polystyrene (PSBr), and poly(methyl acrylate) (PMABr) are prepared by atom transfer radical polymerization (ATRP) and employed in a variety of atom transfer radical coupling (ATRC)‐type reactions to observe the impact of external aromatic faces on the extent of coupling (Xc). In ATRC reactions assisted with the radical trap 2‐methyl‐2‐nitrosopropane (MNP), Xc is nearly unchanged when the electron‐rich benzene co‐solvent (50% v/v with THF) is replaced with the electron‐poor hexafluorobenzene (HFB) for PSBr and PMABr. In the case of PPFSBr, the addition of benzene to the reaction mixture results in far lower extents of coupling (Xc < 0.2). 1H NMR spectra of the radical trap MNP in HFB show greater aggregation to the inactive form, compared to the spectra obtained in benzene. To remove the effect of the radical trap interacting with the aromatic co‐solvent and altering the rate of coupling, traditional ATRC reactions are performed with the same co‐solvent systems and, in this case, HFB results in higher Xc values across all polymer types. This is consistent with HFB pushing the position of the KATRP further toward the active radical, while benzene increases the reactivity of the MNP radical trap. [ABSTRACT FROM AUTHOR]