RAFT radical copolymerization of beta‐pinene with maleic anhydride and aggregation behaviors of their copolymer in aqueous solution

RAFT copolymerization of beta‐pinene and maleic anhydride was successfully achieved for the first time, using 1‐phenylethyl dithiobenzoate as chain transfer agent in a mixed solvent of tetrehydrofuran and 1.4‐dioxane (1:9, v/v) at a feed molar ratio of beta‐pinene to maleic anhydride as 3:7, and the alternating copolymer was prepared with predetermined molecular weight and narrow molecular weight distribution. Furthermore, using former alternating copolymer as a macro‐RAFT agent, block copolymer poly(beta‐pinene‐alt‐maleic anhydride)‐b‐polystyrene was synthesized in a chain extending with styrene. Hydrolysis of this block copolymer under acidic conditions formed a new amphiphilic block copolymers poly(beta‐pinene‐alt‐maleic acid)‐b‐polystyrene whose self‐assembly behaviors in aqueous solution at different pH were investigated through SEM and DLS. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1422–1429     

Reversible addition–fragmentation transfer (RAFT) copolymerization of methyl methacrylate and styrene in miniemulsion

In the reversible addition–fragmentation transfer (RAFT) copolymerization of two monomers, even with the simple terminal model, there are two kinds of macroradical and two kinds of polymeric RAFT agent with different R groups. Because the structure of the R group could exert a significant influence on the RAFT process, RAFT copolymerization may behave differently from RAFT homopolymerization. The RAFT copolymerization of methyl methacrylate (MMA) and styrene (St) in miniemulsion was investigated. The performance of the RAFT copolymerization of MMA/St in miniemulsion was found to be dependent on the feed monomer compositions. When St is dominant in the feed monomer composition, RAFT copolymerization is well controlled in the whole range of monomer conversion. However, when MMA is dominant, RAFT copolymerization may be, in some cases, out of control in the late stage of copolymerization, and characterized by a fast increase in the polydispersity index (PDI). The RAFT process was found to have little influence on composition evolution during copolymerization. The synthesis of the well‐defined gradient copolymers and poly[St‐b‐(St‐co‐MMA)] block copolymer by RAFT miniemulsion copolymerization was also demonstrated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6248–6258, 2004     

Synthesis of well‐defined copolymer of acrylonitrile and maleic anhydride via RAFT polymerization

Well‐defined copolymer of acrylonitrile (AN) and maleic anhydride (MAn) has been successfully synthesized via reversible addition‐fragmentation chain transfer polymerization. The polymerization kinetics and “living”/controlled features were thoroughly studied and confirmed. The thermal properties and spinnability of the prepared copolymers were investigated via differential scanning calorimetry, thermogravimetric analyzer, and electrospinning subsequently. When PAN‐co‐PMAn was used as precursors, nonwoven with “crosslinked” structures was obtained during electrospinning. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5263–5269     

Well‐defined phosphonate‐functional copolymers through RAFT copolymerization of dimethyl‐p‐vinylbenzylphosphonate

Dibenzyltrithiocarbonate‐mediated RAFT polymerization of dimethyl‐p‐vinylbenzylphosphonate and its copolymerization with styrene are studied in order to access well‐defined statistical and block copolymers containing controlled amounts of dimethylphosphonate groups. NMR and SEC analysis of the (co)polymers confirm the controlled character of the polymerizations. ABA triblock copolymers are treated with TMSiBr/MeOH in order to transform the dimethylphosphonate groups into phosphonic acids while keeping the midchain trithiocarbonate group and triblock nature unaffected. Alternatively, the combination of trithiocarbonate aminolysis with TMSiBr/MeOH treatment of the same triblock copolymers leads to phosphonic acid‐functional diblock copolymer counterparts. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2616‐2624     

Radical‐medicated end‐group transformation of amphiphilic methacrylate random copolymers for modulation of antimicrobial and hemolytic activities

This work describes synthesis of antimicrobial methacrylate copolymers by reversible addition‐fragmentation chain transfer (RAFT) polymerization and examines the versatility of this approach for improving chemical optimization to create potent, non‐toxic antimicrobial polymers. Specifically, this study focuses on the radical‐mediated transformation of end group of antimicrobial peptide‐mimetic polymer. RAFT polymerization using 2‐cyano‐2‐yl‐dithiobenzoate provided a statistical methacrylate copolymer consisting of aminobutyl and ethyl groups in the side chains. The following radical‐mediated modification using free radical initiators successfully transformed the ω‐end group of parent copolymer from dithiobenzoate to a cyanoisobutyl or aminoethyl cyanopentanoate group without any significant changes to the polymer molecular weight. In general, the parent polymer and variants showed a broad spectrum of activity against a panel of bacteria, but low hemolytic activity against human red blood cells. The parent copolymer with the dithiobenzoate end‐group showed highest antimicrobial and hemolytic activities as compared with other copolymers. The copolymers caused membrane depolarization in Staphylococcus aureus, while the ability of copolymers for membrane disruption is not dependent on the end‐group structures. The synthetic route reported in this study will be useful for further study of the role of polymer end‐groups in the antimicrobial activity of copolymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 304–312     

Influence of the chemical structure of dithiocarbamates with different N‐groups on the reversible addition–fragmentation chain transfer polymerization of styrene

Polymerizations of styrene with azobisisobutyronitrile initiation or thermal initiation have been performed in the presence of dithiocarbamates with different N‐groups, that is, benzyl 4,5‐diphenyl‐1H‐imidazole‐1‐carbodithioate ( 2a ), benzyl 1H‐1,2,4‐triazole‐1‐carbodithioate ( 2b ), benzyl indole‐1‐carbodithioate ( 2c ), benzyl 2‐phenyl‐indole‐1‐carbodithioate ( 2d ), benzyl phenothiazine‐10‐carbodithioate ( 2e ), benzyl 9H‐carbazole‐9‐carbodithioate ( 2f ), and benzyl dibenzo[b,f]azepine‐5‐carbodithioate ( 2g ). The results show that the structure of the N‐group of dithiocarbamates has significant effects on the activity of dithiocarbamates for the polymerization of styrene. 2a , 2b , 2c , 2d , and 2f are effective reversible addition–fragmentation chain transfer (RAFT) agents for the RAFT polymerization of styrene, and the polymerizations have good living characteristics. However, in the cases of 2e and 2g , the obtained polymers have uncontrolled molecular weights and broad molecular weight distributions. The polymerization rate is markedly influenced by the conjugation structure of the N‐group of the dithiocarbamate, and the polymerization rate of 2b is greater than that of 2a . For 2b , the rate of polymerization seems independent of the RAFT agent concentration. However, a significant retardation in the rate of polymerization can be observed in the case of 2c . 2d is more effective than 2c , and the substitution group of phenyl on this dithiocarbamate has obvious effects on the effectiveness of the controlled polymerization of styrene. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4849–4856, 2005     

Synthesis of comb‐like polystyrene with poly(N‐phenyl maleimide‐alt‐p‐chloromethyl styrene) as macroinitiator

The copolymerization of N‐phenyl maleimide and p‐chloromethyl styrene via reversible addition–fragmentation chain transfer (RAFT) process with AIBN as initiator and 2‐(ethoxycarbonyl)prop‐2‐yl dithiobenzoate as RAFT agent produced copolymers with alternating structure, controlled molecular weights, and narrow molecular weight distributions. Using poly(N‐phenyl maleimide‐alt‐p‐chloromethyl styrene) as the macroinitiator for atom transfer radical polymerization of styrene in the presence of CuCl/2,2′‐bipyridine, well‐defined comb‐like polymers with one graft chain for every two monomer units of backbone polymer were obtained. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2069–2075, 2006     

Cyclopolymerization of α,ω‐heterodifunctional monomers containing styrene and maleimide moieties

A series of α,ω‐heterodifunctional monomers with styrene (St) and maleimide moieties bridged by a varied length of oligo‐ethylene glycol (OEG) linkers were synthesized. Cyclopolymerizations of these monomers through reversible addition–fragmentation chain transfer‐mediated alternating radical copolymerization between intramolecular St and maleimide moieties were investigated. For the monomers with three or more ethylene glycol (EG) units, their cyclopolymerizations can be realized properly in low monomer feeding concentrations, affording well‐defined cyclopolymers with crown ether encircled in their main chains. Importantly, the cyclopolymerizations of monomers with six or seven EG units in the presence of KPF₆ could be enhanced by the supramolecular effects between the OEG linkers and the potassium metal ion. Thus, the monomer feeding concentration could be largely improved, which may benefit preparation of the cyclopolymers with high degrees of copolymerization. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 330–338     

Synthesis and characterization of fluorescence end‐labeled polystyrene via reversible addition‐fragmentation chain transfer (RAFT) polymerization

Fluorescence end‐labeled polystyrene (PS) with heteroaromatic carbazole or indole group were prepared conveniently via reversible addition‐fragmentation chain transfer (RAFT) polymerization using dithiocarbamates, ethyl 2‐(9H‐carbazole‐9‐carbonothioylthio)propanoate (ECCP) and benzyl 2‐phenyl‐1H‐indole‐1‐carbodithioate (BPIC) as RAFT agents. The end functionality of obtained PS with different molecular weights was high. The steady‐state and the time‐resolved fluorescence techniques had been used to study the fluorescence behaviors of obtained end‐labeled PS. The fluorescence of dithiocarbamates resulting PS in solid powder cannot be monitored; however, they exhibited structured absorptions and emissions in solvent DMF and the fluorescence lifetimes of PS had no obvious change with molecular weights increasing. These observations suggested that the polymer chains were possibly stretched adequately in DMF, that is, the fluorescence end group was exposed into solvent molecules and little quenching of excited state occurred upon incorporation into polymer chain. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6198–6205, 2008     

Experimental Requirements for an Efficient Control of Free‐Radical Polymerizations via the Reversible Addition‐Fragmentation Chain Transfer (RAFT) Process

Summary: Reversible addition‐fragmentation chain transfer (RAFT) polymerization is a recent and very versatile controlled radical polymerization technique that has enabled the synthesis of a wide range of macromolecules with well‐defined structures, compositions, and functionalities. The RAFT process is based on a reversible addition‐fragmentation reaction mediated by thiocarbonylthio compounds used as chain transfer agents (CTAs). A great variety of CTAs have been designed and synthesized so far with different kinds of substituents. In this review, all of the CTAs encountered in the literature from 1998 to date are reported and classified according to several criteria : i) the structure of their substituents, ii) the various monomers that they have been polymerized with, and iii) the type of polymerization that has been performed (solution, dispersed media, surface initiated, and copolymerization). Moreover, the influence of various parameters is discussed, especially the CTA structure relative to the monomer and the experimental conditions (temperature, pressure, initiation, CTA/initiator ratio, concentration), in order to optimise the kinetics and the efficiency of the molecular‐weight‐distribution control.

Schematic of the RAFT polymerization.     

Influence of small amounts of addition‐fragmentation capable monomers on polymerization‐induced shrinkage stress

The effects of the addition of small amounts of multifunctional monomers that contain functional groups capable of undergoing addition‐fragmentation during radical polymerizations are investigated. Specifically, up to 6 wt % of phenyl trithiocarbonate (TTC)‐containing diacrylate was added to conventional thiol‐multiacrylate photopolymerizations where its addition led to up to 60% reduction in polymerization‐induced shrinkage stress. The higher levels of TTC achieve the lowest stress though they also significantly depress the polymerization rate. Using up to 0.5 wt % phenyl TTC successfully reduces the stress by nearly 20%, demonstrating the effectiveness of the phenyl TTC, while minimizing the influence that the RAFT activity of the TTC unit has on the polymerization rate. When the polymerization rates of the TTC‐containing resins are increased by changing the incident light intensity, complete acrylate conversion is achieved and the stress remains up to 40% lower in the TTC‐containing resins. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1315–1321     

RAFT polymerization of alternating styrene‐pentafluorostyrene copolymers

Reversible addition‐fragmentation chain‐transfer (RAFT) polymerization was used to control the alternating copolymerization of styrene and 2,3,4,5,6‐pentaflurostyrene. The RAFT polymerization yields a high degree of control over the molecular weight of the polymers and does not significantly influence the reactivity ratios of the monomers. The controlled free‐radical polymerization could be initiated using AIBN at elevated temperatures or using a redox couple (benzoyl peroxide/N,N‐dimethylaniline) at room temperature, while maintaining control over molecular weight and dispersity. The influence of temperature and solvent on the molecular weight distribution and reactivity ratios were investigated. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1555–1559     

Room‐temperature RAFT copolymerization of 2‐chloroallyl azide with methyl acrylate and versatile applications of the azide copolymers

A new vinyl azide monomer, 2‐chlorallyl azide (CAA), has been synthesized from commercially available reagent in one step. The reversible addition fragmentation chain transfer (RAFT) copolymerization of CAA with methyl acrylate (MA) was carried out at room temperature using a redox initiator, benzoyl peroxide (BPO)/N,N‐dimethylaniline (DMA), in the presence of benzyl 1H‐imidazole‐1‐carbodithioate (BICDT). The polymerization results showed that the process bears the characteristics of controlled/living radical polymerizations, such as the molecular weight increasing linearly with the monomer conversion, the molecular weight distribution being narrow, and a linear relationship existing between ln([M]₀/[M]) and the polymerization time. Chain extension polymerization was performed successfully to prepare block copolymer. Furthermore, the azide copolymers were functionalized by Cu^I‐catalyzed “click” reaction with alkyne‐containing poly(ethylene glycol) (PEG) to yield graft copolymers with hydrophilic PEG side chains. Surface modification of the glass sheet was successfully achieved via the crosslinking reaction of the azide copolymer under UV irradiation at ambient temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1348–1356, 2010     

Controlled polymerization of N‐isopropylacrylamide with an activated methacrylic ester

A copolymer of N‐isopropylacrylamide with the N‐hydroxysuccinimide ester of methacrylic acid has found use in a variety of applications. Here we report our efforts to gain control over the molecular weight distribution of this copolymer with controlled radical polymerization methods, such as atom transfer radical polymerization, reversible addition–fragmentation transfer (RAFT), and nitroxide‐mediated polymerization. We have found that RAFT is capable of affording these copolymers with a polydispersity index of 1.1–1.2. Our results for all three polymerizations are reported. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6340–6345, 2004     

Well‐defined polyisoprene‐grafted silica nanoparticles via the RAFT process

The preparation of well‐defined polyisoprene‐grafted silica nanoparticles (PIP‐g‐SiO₂ NPs) was investigated. Surface initiated reversible addition fragmentation chain transfer (SI‐RAFT) polymerization was used to polymerize isoprene from the surface of 15 nm silica NPs. A high temperature stable trithiocarbonate RAFT agent was anchored onto the surface of particles with controllable graft densities. The polymerization of isoprene mediated by silica anchored RAFT with different densities were investigated and compared to the polymerization mediated by free RAFT agents. The effects of different temperatures, initiators, and monomer feed ratios on the kinetics of the SI‐RAFT polymerization were also investigated. Using this technique, block copolymers of polyisoprene and polystyrene on the surface of silica particles were also prepared. The well‐defined synthesized PIP‐g‐SiO₂ NPs were then mixed with a polyisoprene matrix which showed a good level of dispersion throughout the matrix. These tunable grafted particles have potential applications in the field of rubber nanocomposites. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1493–1501     

Synthesis of liquid‐filled nanocapsules via the miniemulsion technique

This study describes the synthesis of well‐defined nanocapsules via the miniemulsion technique. Pentaerythritol tetrakis(3‐mercaptopropionate) (TetraThiol) or 1,6‐hexanediol di(endo, exo‐norborn‐2‐ene‐5‐carboxylate) (DiNorbornene) is used as the oil phase. TetraThiol is encapsulated via the miniemulsion technique without polymerization, as this monomer would simultaneously act as a chain‐transfer agent, and DiNorbornene is encapsulated via miniemulsion polymerization of styrene. Various styrene‐maleic anhydride (PSMA) copolymers and poly(styrene‐maleic anhydride)‐block‐polystyrene (PSMA‐b‐PS) block copolymers were used as surfactant for the synthesis of well‐defined nanocapsules with TetraThiol as the core material. The nanocapsules had a diameter of 150–350 nm and the particle size distribution was narrow. The use of PSMA‐b‐PS block copolymers as surfactant in combination with post‐addition of formaldehyde provided improved stability to the nanocapsules. DiNorbornene was encapsulated via miniemulsion polymerization of styrene, and a stable latex with a bimodal particle size distribution was obtained. The distribution of small particles had a size of 60 nm and the distribution of large particles had a size of 150 nm. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Free‐radical copolymerization of ethyl α‐hydroxymethylacrylate with methyl methacrylate by reversible addition–fragmentation chain transfer

The controlled free‐radical homopolymerization of ethyl α‐hydroxymethylacrylate and copolymerization with methyl methacrylate were performed in chlorobenzene at 70 °C by the reversible addition–fragmentation chain transfer polymerization technique with 2,2′‐azobisisobutyronitrile as the initiator. 2‐Phenylprop‐2‐yl dithiobenzoate and 2‐cyanoprop‐2‐yl dithiobenzoate were used as chain‐transfer agents in the homopolymerization, whereas only the former was used in the copolymerization. All reactions presented pseudolinear kinetics. The effect of the monomer feed ratio on the copolymerization kinetics was examined. The conversion level decreased when the proportion of ethyl α‐hydroxymethylacrylate in the monomer feed was larger. Kinetic studies indicated that the radical polymerizations proceeded with apparent living character according to experiments, demonstrating an increase in the molar mass with the monomer conversion and a relatively narrow molar mass distribution. All copolymers were statistical in chain structure, as confirmed by determinations of the monomer reactivity ratios. The monomer reactivity ratios were determined, and the Mayo–Lewis terminal model provided excellent predictions for the variations of the intermolecular structure over the entire conversion range. Additionally, the chemical modification of poly(ethyl α‐hydroxymethylacrylate) was carried out to introduce glucose pendant groups into the structure. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5618–5629, 2006     

Controlled synthesis of carboxylic acid end‐capped poly(heptadecafluorodecyl acrylate) and copolymers with 2‐hydroxyethyl acrylate

1H,1H,2H,2H‐Heptadecafluorodecyl acrylate (AC8) was polymerized by reversible addition–fragmentation chain transfer and copolymerized with 2‐hydroxyethyl acrylate with the formation of random and block copolymers, respectively. The kinetics of the (co)polymerization was monitored with ¹H NMR spectroscopy and showed that the homopolymerization and random copolymerization of AC8 were under control. As a result of this control and the use of S‐1‐dodecyl‐S‐(α,α′‐dimethyl‐α″‐acetic acid)trithiocarbonate as a chain‐transfer agent, the copolymer chains were end‐capped by an α‐carboxylic acid group. Moreover, the controlled polymerization of AC8 was confirmed by the successful synthesis of poly(1H,1H,2H,2H‐heptadecafluorodecyl acrylate)‐b‐poly(2‐hydroxyethyl acrylate) diblock copolymers, which were typically amphiphilic compounds. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1499–1506, 2007     

Controlled radical copolymerization of β‐pinene and acrylonitrile

The feasibility of the radical copolymerization of β‐pinene and acrylonitrile was clarified for the first time. The monomer reactivity ratios evaluated by the Fineman–Ross method were r_β‐pinene = 0 and r_{acrylonitrile} = 0.66 in dichloroethane at 60 °C with AIBN, which indicated that the copolymerization was a simple alternating copolymerization. The addition of the Lewis acid Et₂AlCl increased the copolymerization rate and enhanced the incorporation of β‐pinene. The first example for the synthesis of an almost perfectly alternating copolymer of β‐pinene and acrylonitrile was achieved in the presence of Et₂AlCl. Furthermore, the possible controlled copolymerization of β‐pinene and acrylonitrile was then attempted via the reversible addition–fragmentation transfer (RAFT) technique. At a low β‐pinene/acrylonitrile feed ratio of 10/90 or 25/75, the copolymerization with 2‐cyanopropyl‐2‐yl dithiobenzoate as the transfer agent displayed the typical features of living polymerization. However, the living character could be observed only within certain monomer conversions. At higher monomer conversions, the copolymerizations deviated from the living behavior, probably because of the competitive degradative chain transfer of β‐pinene. The β‐pinene/acrylonitrile copolymers with a high alternation degree and controlled molecular weight were also obtained by the combination of the RAFT agent cumyl dithiobenzoate and Lewis acid Et₂AlCl. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2376–2387, 2006