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In this research, we developed an efficient approach to prepare hyperbranched polymers at room temperature via phosphazene-base t-BuP2 catalyzed oxa-Michael addition polymerization from commercially available trifunctional hydroxyl and diacrylate monomers. The branching structure of the obtained polymers and the polymerization process were investigated by nuclear magnetic resonance (NMR) spectroscopy and triple-detection size-exclusion chromatography (TD-SEC) analysis. It was revealed that acrylic double bond terminated branched polymers with high molecular weights and high degrees of branching (Mw.MALLS > 2.8 × 105 g mol−1, DB ≥ 0.8) were produced by t-BuP2 catalyzed oxa-Michael addition polymerization of a trimethylolpropane (TMP) with a double molar 1,6-hexanediol diacrylate (HDDA) in DMF at room temperature, even at 0 °C. The study of the branching process showed that t-BuP2 catalyzed oxa-Michael addition branching polymerization is rapid, and that significant branched structures formed when the polymerization was performed at 3 min. Most importantly, the prepared branched polymers can be further post-functionalized via aza- or thio-Michael addition reactions, due to the polymers retaining the acrylic double bond functionality. This research provides a versatile and efficient method for the preparation of hyperbranched polymers from commercially available monomers, and it is feasible to prepare functional branched polymers for application in various fields.

Phosphazene base, t-BuP2, was employed to catalyze the proton transfer polymerization (PTP) of 2-hydroxyethyl acrylate (HEA), and PTP was further combined with ring-opening polymerization (ROP) to exploit a new type of hybrid copolymerization. The studies on homopolymerization showed that t-BuP2 was a particularly efficient catalyst for the polymerization of HEA at room temperature, giving an excellent monomer conversion. Throughout the polymerization, transesterification reactions were unavoidable, which increased the randomness in the structures of the resulting polymers. The studies on copolymerization showed that t-BuP2 could simultaneously catalyze the hybrid copolymerization via the combination of PTP and ROP at 25 °C. During copolymerization, HEA not only provided hydroxyl groups to initiate the ROP of e-caprolactone (CL) but also participated in the polymerization as a monomer for PTP. The copolymer composition was approximately equal to the feed ratio, demonstrating the possibility to adjust the polymeric structure by simply changing the monomer feed ratio. This copolymerization reaction provides a simple method for synthesizing degradable functional copolymers from commercially available materials. Hence, it is important not only in polymer chemistry but also in environmental and biomedical engineering.

We reported a facile and effective method for the preparation of highly branched polymers by combining the concepts of self-condensing vinyl polymerization (SCVP) and iodine transfer polymerization (ITP). This procedure used a chain transfer monomer synthesized in situ from a commercially available chloride compound, p-chloromethylstyrene (CMS). The efficiencies of the halogen exchange from the alkyl chloride (−CH2Cl) to the alkyl iodide (−CH2I) at room and high temperature were studied using CMS and benzyl chloride as model halogenated compounds. The structures of the resulting polymer and the branching behavior were analyzed by nuclear magnetic resonance (NMR) spectroscopy and size-exclusion chromatography (SEC) equipped with a differential refractive index detector, a multiangle laser light scattering detector, and a viscometer detector. The model study using small molecules revealed that −CH2Cl could efficiently halogen exchange with sodium iodide (NaI) at both room and high temperature. The model lin...

The radical polymerization of multivinyl monomers usually provides crosslinking polymers. It is a significant challenge how to control the structure of the polymers and to obtain soluble polymers in a high yield. In this work, the radical branching polymerizations of two asymmetrical divinyl monomers, allyl methacrylate (AMA) and furfuryl methacrylate (FMA), were investigated in detail. Both of the reactivity of the bonds and the weak transfer of isopropyl alcohol (IPA) were used to control the development of branching polymerizations and avoid gelation, without any other additives. As a result, the soluble branched PAMAs and PFMAs with extremely high molecular weights (106∼107) were successfully obtained. The branching factor (g’) of PAMA is very low (0.01–0.02), and that of PFMA is the higher (about 0.3) due to the weaker reactivity of furfuryl groups. Comparing with the results of using thiol chain transfer agent, the chain transfer of IPA had no obvious influence on the chain propagation at the early stage of the polymerizations, but could delay the gelation successfully at the later stage. Furthermore, the development of the branching structure could be studied in detail on the branching factor and rms radius since the gelation process was extended from several minutes to several hours.

Several branched polystyrenes were prepared by free radical emulsion polymerization in the presence of α-mercaptohexyl methacrylate (MHM) as the chain transfer monomers, potassium peroxodisulfate a...

This paper reports a new type of click chemistry via a phosphazene bases-catalyzed oxa-Michael addition of an alcohol to an acrylate. The studies on the reactions between small molecules showed that only 5 mol% phosphazene base, t-BuP2, could catalyze the reaction between the acrylate double bonds and a primary alcohol and drive the reaction to completion within a few minutes under solvent-free conditions at room temperature. Additionally, t-BuP2 was a particularly efficient catalyst for the oxa-Michael addition of secondary alcohols to acrylate double bonds under similar conditions. Moreover, applying this reaction to the synthesis of polymers could successfully afford degradable poly(ester-ether)s with excellent monomer conversions under mild conditions. Throughout the polymerization, transesterification reactions were unavoidable, which increased the randomness in the structures of the resulting polymers. Considering the remarkable features of this method, such as the ready availability of the alcohol substrates, this work provides a simple, easy, and versatile method for synthesizing degradable polymers from commercially available compounds and will be useful in polymer chemistry.

Aliphatic polyesters have been widely used in environmental and biomedical engineering, but a lack of functional groups limits their applications. Here, we reported a facile approach to synthesize vinyl functional polyester via the ring opening copolymerization of e-caprolactone (CL) and allyl glycidyl ether (AGE). NMR analysis confirmed the copolymeric structures and suggested that the copolymerization depended on the epoxide ring of AGE rather than vinyl group. The amount of AGE incorporated into the copolymers (FAGE) increased with the amount of epoxide monomer feed with a maximum incorporation of 16.7%. Increasing temperature helped AGE to incorporate into the copolymer, however, accompanying with lots amount of AGE homopolymers. The resulting copolymer was successfully post-functionalized by thiol-end click, epoxidation, and bromination reactions depending on the reactivity of pendent ally groups. This facile and efficient approach can be used to functionalize biodegradable polymers and synthesize some new polymers under mild conditions.

Here, we report the reversible complexation-mediated copolymerization (RCMcP) of vinyl and divinyl monomers for the synthesis of highly branched polymers. A conventional azo radical initiator, 2,2′-azobisisoheptonitrile (V65), a free-radical polymerization inhibitor (I2), and a highly reactive but inexpensive salt (NaI) were used to initiate and control the polymerization. The highly branched structures and process of branching were confirmed and thoroughly investigated. The reactivity of the vinyl groups incorporated into the copolymer was found to be similar to that of the monomers used in the RCMcP reaction. Large numbers of branched structures occurred when the conversion of MMA (conv.MMA) reached 56.6%, at which point the amount of pendant vinyl groups in the polymer reached a maximum value. The most significant branching occurred when the conv.MMA approached 90% because of intermolecular reactions between macromolecules. The polymerization reaction can also be performed without deoxygenation, with no obvious prolongation of induction. This work provides a simple, easy, and versatile method for the synthesis of highly branched polymers from commercially available compounds.

In this work, reversible complexation-mediated polymerization (RCMP) was modified to suit self-condensing vinyl polymerization (SCVP) aimed at the synthesis of highly branched polymers. For this purpose, two azo-containing pre-inimers with divinyl (DMACPO) or monovinyl (MACPO) substitution groups were synthesized and copolymerized with methyl methacrylate (MMA). The effects of the pre-inimer structure, the feed ratio, and oxygen on the monomer conversions and on the degree of branching of the obtained polymers were investigated thoroughly. The polymerization process and the branching behaviour were also studied in detail. The study of the DMACPO system revealed that the branched structures were synthesized from the beginning of the polymerization and that substantial branching occurred when the MMA conversion reached 54.7%. At the end of the polymerization, the MMA conversion was greater than 80%. The use of a small amount of additional azo initiator substantially increased the CC bond content among the inimers and the MMA conversion, affording polymers with a high degree of branching. The study of the MACPO system suggested that the monovinyl-functional inimer was much more effective than the divinyl-functional inimer, as the MMA conversion reached as high as 98.0% without inducing gelation. Moreover, the present synthesis could be conducted without additional deoxygenation irrespective of the pre-inimer employed. The current work provides a simple, easy, and versatile method for the synthesis of highly branched polymers from commercially available compounds and will facilitate the application of this method in various highly branched polymer syntheses.

Several inverse emulsions were prepared with different hydrophilic-lipophilic balance (HLB) values using different water/oil ratios, temperatures and monomer and emulsifier concentrations by uniform stirring for more than 30 min. The stability of inverse emulsion was characterized by centrifugal coefficient. The emulsion form, either oil/water (O/W) or water/oil (W/O) was characterized by optical microscope and conductivity measurements. The results showed that HLB value, water/oil ratio and temperature could have an effect on the emulsion stability and emulsion form. When the HLB value of emulsifier is about 8.4, the water to oil ratio is about 1:1 and the temperature is at about 25 °C, inverse emulsion in the form of water in oil (W/O) was found to be the most stable. Here, the stablilty of emulsions was studied in relation to temperature and we found that 25 °C (room temperature) is the best for obtaining the most stable inverse emulsion, which is also most suitable for the redox initiation in this system. In the present study, we showed that temperature has a significant influence on the structure morphology and stability of inverse emulsion and hence, it is necessary to select the appropriate reaction temperature for inverse emulsion polymerization. This is a novel result. A decrease of the content of hydroxyethyl methacrylate in aqueous solution with an increase of emulsifier concentration in emulsion was found to elevate the stability of inverse emulsion. The addition of trace electrolytes in the emulsion, however, led to greatly reduced stability of the inverse emulsion.

It is believed that polymer chains mainly terminate through bimolecular termination in free-radical polymerization, however, there is few convincing evidence to support it. In benzoyl peroxide (BPO) initiated styrene free-radical polymerization, our studies demonstrate that polymer chain terminates dominantly through primary radical termination rather than by bimolecular termination as described in polymer textbooks. Even at very high primary radical concentration or at very low monomer concentration, primary radical termination still dominates (FPRT&CTI>70%) besides the occurrence of some bimolecular coupling terminations. Two kinds of model polymers were prepared, one for bimolecular coupling termination, and the other for primary radical termination. The 1H-, 13C-, DEPT135-, and 2D HSQC NMR spectra of the polystyrene initiated by BPO are almost the same as those of the model polystyrene for primary radical termination, but they are quite different from those of the model polystyrene for bimolecular coupling termination, demonstrating directly that primary radical termination rather than bimolecular coupling termination dominates in BPO-initiated styrene free-radical polymerization.

A novel methacrylate monomer containing azobenzene chromophore and tetrazole moiety, 4′-(2-methacryloxyethyl)methylamino-4-(5-chlorotetrazol-1-yl)azobenzene (MACA), was synthesized and polymerized to form homopolymer (PMACA) via reversible addition-fragmentation chain transfer (RAFT) polymerization using 2-cyanoprop-2-yl dithiobenzoate (CPDB) as the RAFT agent and azobisisobutyronitrile (AIBN) as an initiator in dimethyl formamide (DMF) solution. Meanwhile, block copolymers (PMMA-b-PMACAs) were successfully obtained by RAFT polymerization of MACA using PMMA as the macro-RAFT agent and AIBN as an initiator. Gel permeation chromatography (GPC) characterization indicated that polymers with well-controlled molecular weights and narrow molecular weight distributions (Mw/Mns

Vinyl-functionalized hyperbranched polymers (HBPs) have attracted much attraction because their pendant vinyl groups can be further modified for a required application. However, the syntheses of these polymers are difficult, because the cross-linking is inevitable during the polymerization reaction. The present work reports a new, facile, one-step strategy for the synthesis of vinyl-functionalized HBPs via the self-condensing anionic copolymerization of commercially available allyl methacrylate and hydroxyethyl methacrylate with a monomer conversion approaching 100% at room temperature. The hyperbranched structures were confirmed by triple-detection size exclusion chromatography. The pendent vinyl groups of the resulting polymer were successfully modified by a “thiol-ene” reaction. This method provides a facile approach for preparing vinyl-functionalized HBPs with excellent monomer conversions under mild conditions, and will be useful in materials chemistry.

Branched styrene–acrylic resins were prepared through radical polymerization using cheap 2-(3-mercaptopropionyloxy) ethyl methacrylate (MPOEM) as the chain transfer monomer (CTM). The monomers were added dropwise into the reaction vessel containing xylene at 135°C to obtain styrene–acrylic resins. The formation of branching and the molecular weight were analyzed using triple detection size exclusion chromatography (TD-SEC). The viscosities of the resins were characterized using rotational rheometer and Grignard tube viscometer. By adjusting the dosage of MPOEM and the initiator, a series of branched styrene–acrylic resins were obtained. Generally, the viscosity and the flow ability of the resin were improved evidently when branching was introduced. At the mole ratio of monomer to MPOEM of 100/0.1, the branched styrene–acrylic resin showed 51% decrease in zero-shear viscosity and 62% increase in flow ability, compared with the linear analogues with similar molecular weight at 70% solid content.

Self-condensing vinyl polymerization (SCVP) provides an efficient approach for synthesis of hyperbranched polymers. However, most of the inimers employed for SCVP need to be synthesized before use. Here, we report a facile strategy to synthesize hyperbranched polymers under mild conditions by using a commercially available hydroxyl-substituted methacrylate as the inimer. The hyperbranched structures of the resulting polymers were confirmed by nuclear magnetic resonance, differential scanning calorimetry and size-exclusion chromatography equipped with online light scattering and viscosity detectors. The synthesis can be performed under mild reaction conditions. Particularly, this approach can be applied to not only the SCVP of vinyl monomers but also the self-condensing ring-opening polymerization of cyclic esters for preparation of hyperbranched polyesters. The present study provides a facile strategy to synthesize hyperbranched polymers.

Branched poly (styrene-co-acrylonitrile) was prepared by atom transfer radical polymerisation (ATRP) of styrene (St) and acrylonitrile (AN) with the feed composition of 0·5 using β-bromoethyl benzene (BEB) as the initiator and divinylbenzene (DVB) as the branching agent. The polymerisation kinetics and the development of branching were studied by gas chromatography (GC), triple detection size exclusion chromatography (TD-SEC) and proton nuclear magnetic resonance (1H-NMR) spectroscopy. The primary chains with the pendent vinyl groups were formed dominantly at a monomer conversion of less than 50%. The pendent vinyl group participated in the polymerisation, which resulted in the formation of branching structure accompanied by a rapid increase in molecular weight and a broadening in its distribution. The branching chains developed gradually as the molecular weight increased. The copolymers of higher molecular weights had higher branching degree than those of lower molecular weights.

Branched poly(acrylonitrile-co-vinyl acetate) [P(AN-co-VAc)] was prepared through radical polymerization using new 2-(3-mercaptopropionyloxy) ethyl methacrylate (MPOEM) as a chain transfer monomer (CTM) in sodium thiocyanate (NaSCN) aqueous solution. The development of branching and the changes of molecular weight were analyzed using triple detection size exclusion chromatography (TD-SEC). Below 50% monomer conversion in the presence of MPOEM, the weight average molecular weight (Mw.MALLS) of the copolymer increased with conversion and the molecular weights of the primary chains were much higher. The Zimm branching factor (g′) was lower than one and decreased with increasing conversion, and this result illustrated that the branched chains were formed and the highly branched structures were obtained very fast even at lower monomer conversion. While above 50% monomer conversion in conjunction with complete MPOEM consumption, Mw.MALLS slightly decreased with increasing monomer conversion and almost reached a constant at the end while PDI increased quickly. The g′ slightly increased and then remained constant with increasing conversion, which indicated that the branching degree was invariable in the absence of MPOEM. The zero-shear viscosity and glass transition temperature of branched P(AN-co-VAc)s were lower than those of their linear analogues, which further confirmed the formation of branched P(AN-co-VAc)s. Furthermore, these branched P(AN-co-VAc)s were found to have higher thermal stability than their linear counterparts. These highly branched P(AN-co-VAc)s with lower viscosity and higher thermal stability are amenable for environmentally benign processing with less solvent.

An approach to branched vinyl polymers through radical polymerization in the presence of 3-mercaptohexyl methacrylate (MHM) as the chain transfer monomer is reported in this paper. In the case of polymerization at styrene100–MHM5.0–AIBN2.0, the molecular weight increased with conversion and reached a value of >7.3 × 105 g/mol at 99% conversion; in addition, the Zimm branching factor, g′, was less than 1 and decreased with conversion, when the formation of the branched chain and development of branching was supposed. The bridging units in the obtained polymer, generating from MHM, were cleaved to yield the primary chains. These results have confirmed the formation of branched polymers. Moreover, this study successful prepared branched poly(methyl methacrylate) and poly(vinyl acetate). This methodology proposes good prospects for scaling-up and thereby offers a wide range of branched vinyl polymers at low cost.

The branching copolymerization of styrene and acrylonitrile with divinyl benzene as the branching agent was carried out using atom transfer radical polymerization. Nuclear magnetic resonance and triple detection size exclusion chromatography were used to analyze the reaction. The results suggest that the coupling reaction mainly takes place between the primary chains, forming slightly branched chains in the early stages. The coupling reaction between the branched chains becomes significant at the middle stages, forming highly branched chains. The reaction system consists of primary chains, slightly branched chains containing two primary chains and highly branched chains comprised of more than three primary chains. The weight fraction of the branched chains increases expectedly with monomer conversion.

The branching copolymerization of styrene with triethylene glycol dimethacrylate (tri-EGDMA) as the branching agent was carried out using atom transfer radical polymerization (ATRP) in anisole at 90 °C. The resulting copolymers were analyzed using 1H NMR and triple detection size exclusion chromatography (TD-SEC). The NMR analysis shows that the pendent vinyl groups react even in the early stages of the polymerization. Analysis of the changes in the molecular weight and polydispersity of the copolymers suggests that the reaction system contains three components: the primary chains, the slightly branched chains comprising of two primary chains, and the highly branched chains consisting of more than three primary chains. The coupling reaction mainly takes place between the primary chains, resulting in the slightly branched chains in the early stages of the reaction, the weight fraction of the branched chains and the degree of branching increase gradually with monomer conversion, highly branched chains mainl...

BACKGROUND: Although several methods have been reported for the preparation of hyperbranched cationic polyelectrolytes (HCPs), their applicability is limited. A convenient, facile strategy based on atom transfer radical polymerization (ATRP) of N,N-dimethyl-N-(2-methacryloyloxy)ethyl(2-bromoisobutyryloxy)ethylammonium bromide (DMEAB) with N,N-dimethyl-N-ethyl-N-methacryloyloxyethylammonium bromide (DEMAB) is therefore proposed to prepare their hyperbranched copolymer (PDEMAB). RESULTS: NMR spectroscopy was used to confirm the hyperbranched architecture and to estimate the number-average degree of polymerization (DPn) of the hyperbranched PDEMAB. A kinetic study showed that DPn of the hyperbranched PDEMAB increased very slowly in the initial stage, but increased in an exponential manner during the later phase. When a lower [DEMAB]:[DMEAB] ratio was used, DPn increased much faster than when a higher ratio was used. The CuBr/2,2′-bipyridine complex showed good catalytic activity while FeCl2/aliphatic multi-amine complexes led to crosslinking. For the viscometry of the aqueous solution, although c1/2 − (ηsp/c)−1 fitted well, the Fuoss equation might not be applicable for HCPs. A rheological study showed that the HCPs exhibited an extremely low viscosifying effect, in contrast to their linear analogues. CONCLUSION: The aqueous self-condensing ATRP of DMEAB with DEMAB (and other counterparts) readily led to HCPs. Such a strategy could also be extended to other monomers such as vinylpyridine and vinylimidazole. Copyright © 2009 Society of Chemical Industry

Polymers bearing pendant vinyl groups have attracted significant attraction because they can be further modified for required applications, but their syntheses are still a big challenge. Herein, allyl methacrylate was catalyzed using a phosphazene base to homopolymerize or copolymerize with 2-(N, N-dimethylamino) ethyl methacrylate, affording vinyl functional polymers, which were further successfully tailored by the thiol–ene coupling reaction. The result showed that both the homopolymerizations and copolymerizations could proceed at room temperature with very high monomer conversions. The contents of pendant double bonds in the copolymers were approximately equal to the monomer feeds, but the LCST of the statistical copolymers linearly decreased with increasing AMA content. This strategy offered a new scalable and facile strategy for vinyl functional polymers, would have a wide practical application in many fields. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42758.

An approach to enhancing the volumetric expansion on polymerization of spirobislactone is proposed. This approach suggests a molecular modification of spirobislactone through attaching a rigid pendant segment bearing maleimido group to its aromatic ring. An additional volumetric expansion is achieved from loose molecular packing in cured resins due to the steric hindrance effect among rigid pendent segments. Thus a new monomer, maleimido-functionalized spirobislactone (MFS), is prepared. In order to evaluate the volumetric expansion of MFS during curing, tetraglycidyl 4,4′-diamino diphenyl methane (TGDDM) is employed to cure with MFS. The volumetric expansion of MFS on curing is measured to be 12.3%, higher than that of net spirobislactone monomer. The existence of loose molecular packing in MFS/epoxy cured resins is demonstrated by morphology observation of the cured resin stained by the phosphotungstic acid (PTA), and the stained regions are observed to be nanoparticles. Such a cured resin, prepared from 20 mol% of MFS and 80 mol% of TGDDM epoxy resin, shows excellent toughness (Charpy impact strength 13,000 J/m2) and good mechanical strength (flexural strength 120 MPa, storage flexural modulus 4.2 GPa). Its glass transition temperature by dynamic mechanical thermal analysis (DMA) attains 227 °C, much higher than that of the cured resin from net spirobislactone and epoxy resin.

Radical polymerization with 3-mercapto hexyl methacrylate as the chain transfer monomer (CTM) to prepare branched vinyl polymers with high molecular weights and relatively narrow polydispersities has been carried out in aqueous emulsion. Potassium persulfate was used as the initiator, and sodium dodecyl benzene sulfate or hexadecyl trimethyl ammonium bromide was used as the emulsifier. The obtained polymers were characterized using NMR and size exclusion chromatography. Compared with polymers obtained from solution polymerization and results reported in the literature, branched polymers can be prepared at higher monomer/branching monomer feed ratios (100/25) with high monomer conversion (usually >95%) without gelation. The obtained branched polymers also showed considerably higher molecular weights and relatively narrower polydispersities at the same feed ratio of monomer/branching monomer. The unique radical termination mechanism in emulsion reaction determines that soluble branched polymers with high molecular weight and relatively narrow polydispersity can be prepared at a wide range of monomer/CTM feed ratios without gelation.

Polymerization behaviors and polymer branching structures in atom transfer radical polymerizations of styrene with 1,6-bismaleimidohexane (BMIH), tri-ethylene glycol dimethacrylate (tri-EGDMA) and divinylbenzene (DVB) as the branching agents have been studied, the mole ratio of monomer to branching agent is 30/1.0. Their polymerization behaviors are quite different because of the different levels of interaction between styrene and the branching agents. The charge transfer complex effect between BMIH and styrene causes core-formation. The DVB system exhibits the slowest evolution of branching because there is no interaction between styrene and DVB. The branching structure indicator b(g′ = gb) from the Zimm branching factor at the same molecular weight proves that polymers formed in the tri-EGDMA and DVB systems are randomly branched molecules because tri-EGDMA and DVB were randomly distributed in their primary chains, while the BMIH system contained randomly branched molecules besides the star-like molecules due to the subsequent coupling reactions between the branched molecules after core-formation.