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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.

The ring-forming behavior of polymers with an odd number of arms in highly dilute solutions has been studied using tri-arm polystyrene (PSt3) as a model through combining atom transfer radical polymerization (ATRP) and atom transfer radical coupling (ATRC) technologies. The star polymer, PSt3, with three arms and a central core was obtained by ATRP of styrene using a designed initiator with three active Br terminals and ester groups, followed by the Br terminal–Br terminal radical coupling of PSt3, which was implemented via intramolecular ATRC under high dilution conditions. A tadpole-shaped cyclic polymer (tadpole-PSt) was successfully prepared, proving that there no intermolecular side reactions that occur during the intramolecular ATRC of PSt3. Interestingly, the tadpole-PSt not only possesses a cyclic topology, but also contains a living chain, in contrast to other cyclic analogues that have been previously reported. Finally, the tadpole-PSt was used as a building block to construct a type of barbell polymer (barbell-PSt) by removing most of the solvent via vacuum distillation at the end of the intramolecular ATRC of PSt3. Size exclusion chromatography, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, 1H nuclear magnetic resonance spectroscopy and hydrolysis experiments proved that high-purity cyclic polymers (tadpole-PSt and barbell-PSt) were successfully prepared. The thermal properties of the cyclic and star polymers were analyzed using differential scanning calorimetry and thermogravimetric analysis. The results demonstrated that the formation of a cyclic topology makes a huge contribution to the increase in the glass transition temperature (Tg) and thermal stability of the polymer.

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.

The anionic polymerization of methyl methacrylate (MMA) was carried out using phosphazene base t-BuP4 and ethyl acetate (EA) as the catalyst and the initiator, respectively. Gas chromatography (GC), size exclusion chromatography (SEC) measurements, and nuclear magnetic resonance (NMR) analyses were used to reveal the polymerization mechanism and to confirm the polymer structure. The results confirmed the proposed polymerization mechanism and the polymer structure, while the initiator efficiency was low. Meanwhile, the initiation by methoxy anion coming from hydrolysis of the ester bond in MMA was also observed. As a result, there is a marked deviation between the theoretical molecular weight and the measured molecular weight, and it is essential to carry out the polymerization at excessive dosage of t-BuP4 for preparing polymers with narrow molecular weight distribution.

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...

This work aims to elucidate how the branching effect of macromonomer influences the polymerization, structural features, and solution properties of ABn long-subchain hyperbranched polymers (LHPs). ...

In this study, filaments comprising natural silk fibroin microparticles (NSFP) and biomedical polyurethane (BPU) were prepared via wet-spinning as a reusable-controlled drug-delivery system. The rheological properties of the spinning solution were studied to examine the effect of NSFP on the BPU/NSFP filament formation. The influences of NSFP content and spinning conditions on the morphology, molecular interactions, mechanical properties, and swelling performance of BPU/NSFP filaments were also investigated. The morphology and mechanical property studies showed that NSPF and BPU exhibit good compatibility. The capacity of the BPU/NSFP filaments as drug loading carriers and drug release behavior were studied by spectroscopy. The presence of NSFP in the drug controlled system increase the drug loading amount and enhance the drug release time. This paper presents a well-designed manufacturing method for preparing BPU/NSFP filaments with good controlled drug delivery.

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.

Polyvinyl alcohol (PVA) hydrogels, due to their excellent tissue viscoelasticity and biocompatibility, are widely used in biomedical fields e.g. tissue engineering. However, their poor mechanical properties greatly limit their applications, especially as load-bearing implants in the body. To address this issue, we first synthesize photocrosslinkable PVA-glycidyl methacrylate (PVAGMA) with the extremely low substitution degree (DS = 0.01) of methacryloyl groups, which can undergo chemical crosslinking to form a hydrogel network with good compression performance. Microcrystalline cellulose (MCC)/PVAGMA hydrogels are subsequently fabricated by photopolymerization approach followed by physical crosslinking with tannic acid (TA) as a cross-linking agent. By combing chemical and physical crosslinking, the double crosslinked PVA microcomposite hydrogels exhibit excellent tensile/compression strengths. Specifically, the hydrogels present 23-fold, 20-fold, and 25-fold increase in fracture stress, elastic modulus, and toughness respectively, compared to the pure PVAGMA hydrogels. Notably, a hydrogel with the optimum composition can lift a weight of 3.775 kg, which is about 2220 times of its own weight. Moreover, the hydrogels are cytocompatible at a relatively low extraction concentration, demonstrating their potential in biomaterials.

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.

In this paper, we report radical polymerization in the presence of a peroxide monomer for the preparation of branched vinyl polymers. The peroxide monomer, tert-butyl peroxyacetate methacrylate (BPAMA), was designed and prepared in high purity from commercially available reagents via classic organic reactions. Triple-detection size-exclusion chromatography (TD-SEC) measurements, NMR analyses, and hydrolysis experiments were used to reveal the polymerization procedure and to confirm the branching structure of the prepared polymers. Branched polymers of styrene, methyl methacrylate (MMA), and vinyl acetate (VAc) were prepared under solvent-free conditions through radical polymerization in the presence of a peroxide monomer. Furthermore, radical polymerization in the presence of the peroxide monomer can be operated in a simple polymerization composition involving only the peroxide monomer BPAMA with MMA or VAc. The obtained branched polymers exhibited high molecular weights (Mw.MALLS > 106 g mol−1) and relatively narrow molecular weight distributions (2.5 ≤ PDI ≤ 6.8). Generally, radical polymerization in the presence of a peroxide monomer as the initiator and the branching agent can make the preparation of branched vinyl polymers almost equally as facile as the preparation of their linear analogs. This approach is applicable to a wide variety of monomers and can be performed with a simple polymerization composition in the bulk under moderate conditions compared with the reported strategies.

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.

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

Both temperature and light stimuli-responsive 4-propoxyazobenzene-terminated poly( N -isopropylacrylamide)s (PNIPAMs) were successfully synthesized by the atom transfer radical polymerization (ATRP) of NIPAM. 1 H NMR and UV– vis absorption spectra indicated rapid photoisomerization rate of 4-propoxyazobenzene moiety. Interestingly, the lower critical solution temperature (LCST) for PNIPAM aqueous solution clearly decreased after UV irradiation, and the repeated LCST difference (ΔT maxy = 5 °C) depended on both the number-average molecular weight and amount of azobenzene chromophore. Dynamic light scattering (DLS) and static light scattering (SLS) measurements showed that the PNIPAM aqueous solution could self-assemble into nano-micelles with 4-propoxyazobenzene as the hydrophobic cores and PNIPAM chains as the hydrophilic shells. UV irradiation induced the increase of particle size due to the formation of much looser cores of cis -azobenzene. TEM images showed the presence of both nanorods and spherical micelles. After UV irradiation, the unstable spherical micelles transformed to metastable nanorods, then to longer rods, and finally the longer rods began to transform to flake-like particles via horizontal inter-rod aggregation above LCST.

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.

A novel well-defined linear poly(ε-caprolactone) (P1) containing terminal azobenzene and ethyne groups was successfully synthesized through tin-catalyzed ring-opening polymerization of ε-caprolactone in the presence of N,N′-bis(2-hydroxyethyl)-4-(3-ethynylphenylazo)aniline (BHA) in bulk. Subsequent reactions allowed the synthesis of the corresponding bromoester end-functionalized polymer (P2), which was converted into AB2 type polymer (P3) containing terminal azide groups with NaN3. Consequently, hyperbranched poly(ε-caprolactone) (HPCL) was prepared with AB2 macromonomer (P3) by “click” chemistry under the catalysis of CuSO4·5H2O/sodium ascorbate/H2O. The structure of the resultant HPCL was characterized by gel permeation chromatography (GPC), proton nuclear magnetic resonance (1H-NMR), ultraviolet-visible (UV-Vis) spectroscopy and fourier transform infrared spectroscopy (FT-IR). Thermal and crystallization properties of P1 and HPCL were further studied by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarised optical microscopy (POM). These results indicated that the crystallinity of HPCL was slightly lower than that of P1 due to the hyperbranched structure of HPCL. Additionally, the photo-induced trans-cis isomerization behaviors of BHA, P1 and HPCL containing terminal azobenzene were investigated in chloroform solution, and the photoisomerization rate constant (kexp) of small molecule (BHA) was nearly three times faster than that of polymers P1 and HPCL, which was due to the sterically hindering effect of the polymer-chain configuration.

Radical solvent-free suspension polymerization of styrene with 3-mercapto hexyl-methacrylate (MHM) as the branching monomer has been carried out using 2,2′-azobisisobutyronitrile (AIBN) as the initiator to prepare branched polymer beads of high purity. The molecular weight and branching structure of the polymers have been characterized by triple detection size exclusion chromatography (TD-SEC), proton nuclear magnetic resonance spectroscopy (1H-NMR), and Fourier transform infrared spectroscopy (FTIR). The glass transition temperature and rheological properties have been measured by using differential scanning calorimetry (DSC) and rotational rheometry. At mole ratios of MHM to AIBN less than 1.0, gelation was successfully avoided and branched polystyrene beads were prepared in the absence of any solvent. Branched polystyrene has a relatively higher molecular weight and narrower polydispersity (Mw.MALLS = 1,036,000 g·mol−1, Mw/Mn = 7.76) than those obtained in solution polymerization. Compared with their linear analogues, lower glass transition temperature and decreased chain entanglement were observed in the presently obtained branched polystyrene because of the effects of branching.

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.

Ultrafast preparation of branched poly(methyl acrylate) (BPMA) with high-molecular weight through single electron transfer living radical polymerization (SET-LRP) of inimer at 25°C has been attempted, atom transfer radical polymerization (ATRP) at 60°C was also carried out for comparison. Gas chromatography, proton nuclear magnetic resonance, and triple detection size exclusion chromatography were used to analyze these polymerizations. As expected, SET-LRP system showed much faster polymerization rate than ATRP system, the calculated apparent propagation rate constants (kpapp) are 3.69 × 10−2 min−1 and 6.23 × 10−3 min−1 for SET-LRP and ATRP system, respectively. BPMA with high-molecular weight (Mw.MALLS = 86,400 g mol−1) compared with that in ATRP (Mw.MALLS = 61,400 g mol−1) has been prepared. POLYM. ENG. SCI., 54:1579–1584, 2014. © 2013 Society of Plastics Engineers

Hyperbranched poly(N-isopropylacrylamide)s (HBPNIPAMs) end-capped with different azobenzene chromophores (HBPNIPAM-Azo-OC3H7, HBPNIPAM-Azo-OCH3, HBPNIPAM-Azo, and HBPNIPAM-Azo-COOH) were successfully synthesized by atom transfer radical polymerization (ATRP) of N-isopropylacrylamide using different azobenzene-functional initiators. All HBPNIPAMs showed a similar highly branched structure, similar content of azobenzene chromophores, and similar absolute weight/average molecular weight. The different azobenzene structures at the end of the HBPNIPAMs exhibited reversible trans-cis-trans isomerization behavior under alternating UV and Vis irradiation, which lowered the critical solution temperature (LCST) due to different self-assembling behaviors. The spherical aggregates of HBPNIPAM-Azo-OC3H7 and HBPNIPAM-Azo-OCH3 containing hydrophobic para substituents either changed to bigger nanorods or increased in number, leading to a change in LCST of −2.0 and −1.0 °C, respectively, after UV irradiation. However, the unimolecular aggregates of HBPNIPAM-Azo were unchanged, while the unstable multimolecular particles of HBPNIPAM-Azo-COOH end-capped with strongly polar carboxyl groups partly dissociated to form a greater number of unimolecular aggregates and led to an LCST increase of 1.0 °C.

Poly(ϵ-caprolactone-co-tert-butyl methacrylate) (CL-co-BMA) random copolymer is synthesized via hybrid copolymerization with 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phophoranylidenamino]-2Λ5,4Λ5-catenadi(phosphazene) (t-BuP4) as the catalyst. The copolymer is hydrolyzed into poly(ϵ-caprolactone-co-methacrylic acid) (CL-co-MAA), a charged copolymer. Nuclear magnetic resonance, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis measurements indicate that cyclic ester and vinyl monomer form a random copolymer. The degradation of the copolymers has also been studied by use of quartz crystal microbalance with dissipation.

Poly(e-caprolactone-co-ethylene carbonate-co-ethylene oxide) (CL-co-EC-co-EO) copolymer was synthesized via ring-opening copolymerization of e-caprolactone (CL) and 1,3-dioxolan-2-one with a metal-free phosphazene catalyst (t-BuP4). The monomer conversion and molecular weight in CL-co-EC-co-EO copolymer were characterized by nuclear magnetic resonance and gel permeation chromatography, respectively. Moreover crystallization behavior of CL-co-EC-co-EO copolymer was investigated by differential scanning calorimeter and wide-angle X-ray diffraction. The enzymatic degradation of the copolymer has been investigated by quartz crystal microbalance with dissipation. Our studies demonstrate that as PCL content in the copolymer decreases, the degree of crystallinity and crystal size decrease, while the enzymatic degradation rate increases. The copolymer exhibits layer-by-layer degradation.

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.

Copolymerization of e-caprolactone and methyl methacrylate with (1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phophoranylidenamino]-2Λ5,Λ5-catenadi(phosphazene) (t-BuP4) as the catalyst has been studied. Nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC) measurements indicate that the cyclic ester and vinyl monomer form a random copolymer. Thermogravimetric analysis (TGA) measurements demonstrate that such a random copolymer exhibits a decomposition temperature higher than those of the corresponding homopolymers. The present study reveals a “hybrid copolymerization” i.e., a combination of vinyl polymerization and ring-opening polymerization, which makes the incorporation of cyclic and vinyl monomers into the same polymer chain possible. Hybrid copolymerization is expected to produce a number of new interesting polymers.

Copolymers of methyl methacrylate (MMA) and acrylate terminated poly(ethylene oxide-co-ethylene carbonate) (PEOC) macromonomer (PEOCA) were synthesized, and the degradation of the polymers was investigated by use of quartz crystal microbalance with dissipation (QCM-D). It is shown that the polymeric surface exhibits degradation in seawater depending on the content of the side chains. Field tests in seawater show that the surface constructed by the copolymer can effectively inhibit marine biofouling because it can be self-renewed due to degradation of the copolymer.

Poly[(ethylene carbonate)-co-(ethylene oxide)] is synthesized by ROP of 1,3-dioxolan-2-one using 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phosphoranylidenamino]-2Λ5,Λ5-catenadiphosphazene as the catalyst. NMR spectroscopy shows that the copolymer chain consists of EO-EC-EO-EO sequences. GPC measurements indicate a PDI of 1.43–1.66 and show that the molecular weight increases with monomer conversion. Thermal analysis demonstrates that the copolymer is amorphous with a glass transition temperature of about –42 °C and an onset decomposition temperature of about 200 °C.

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...

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.

The novel hyperbranched poly(methyl acrylate)-block-poly(acrylic acid)s (HBPMA-b-PAAs) are successfully synthesized via single-electron transfer-living radical polymerization (SET-LRP), followed with hydrolysis reaction. The copolymer solution could spontaneously form unimolecular micelles composed of the hydrophobic core (PMA) and the hydrophilic shell (PAA) in water. Results show that the size of spherical particles increases from 8.18 to 19.18 nm with increased pH from 3.0 to 12.0. Most interestingly, the unique regular quadrangular prisms with the large microstructure (5.70 μm in length, and 0.47 μm in width) are observed by the self-assembly of unimolecular micelles when pH value is below 2. Such self-assembly behavior of HBPMA-b-PAA in solution is significantly influenced by the pH cycle times and concentration, which show that increased polymer concentration favors aggregate growth.

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.

We have synthesized nylon 3 via ring opening polymerization of 2-azetidinone (β-lactam) with 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)- phosphoranylidenamino]-2Λ5,4Λ5-catenadi(phosphazene) (t-BuP4) as the catalyst in a mixture of dimethylacetamide (DMAc) and LiCl. The polymers have been characterized by nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), laser light scattering (LLS) and viscometry. The synthesized nylon 3 is a linear and crystalline polymer with a molecular weight as high as 105 g mol−1. The intrinsic viscosity ([η]) relates to the weight average molecular weight (Mw) as [η] = 1.02 × 10−4Mw0.91. The effects of solvent, temperature and catalyst concentration on the polymerization have been examined. The molecular weight and yield increases with the amount of LiCl in the polymerization mixture, but both of them decrease with temperature at a temperature above 50 °C. As the catalyst concentration increases, the yield and the molecular weight of nylon 3 decrease. The possible mechanism for the initiation of polymerization is discussed.