Surface functionalized nano‐objects from oleic acid‐derived stabilizer via non‐polar RAFT dispersion polymerization

Surface functionalization in a nanoscopic scaffold is highly desirable to afford nano‐particles with diversified features and functions. Herein are reported the surface decoration of dispersed block copolymer nano‐objects. First, side‐chain double bond containing oleic acid based macro chain transfer agent (macroCTA), poly(2‐(methacryloyloxy)ethyl oleate) (PMAEO), was synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization and used as a steric stabilizer during the RAFT dispersion block copolymerization of benzyl methacrylate (BzMA) in n‐heptane at 70 °C. We have found that block copolymer morphologies could evolve from spherical micelles, through worm to vesicles, and finally to large compound vesicles with the increase of solvophobic poly(BzMA) block length, keeping solvophilic chain length and total solid content constant. Finally, different thiol compounds having alkyl, carboxyl, hydroxyl, and protected amine functionalities have been ligated onto the PMAEO segment, which is prone to functionalization via its reactive double bond through thiol‐ene radical reactions. Thiol‐ene modification reactions of the as‐synthesized nano‐objects retain their morphologies as visualized by field emission‐scanning electron microscopy. Thus, the facile and modular synthetic approach presented in this study allowed in situ preparation of surface modified block copolymer nano‐objects at very high concentration, where renewable resource derived oleate surface in the nanoparticle was functionalized. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 263–273     

Aqueous RAFT polymerization of 2‐aminoethyl methacrylate to produce well‐defined,primary amine functional homo‐ and copolymers

We report the direct homopolymerization and block copolymerization of 2‐aminoethyl methacrylate (AEMA) via aqueous reversible addition‐fragmentation chain transfer (RAFT) polymerization. The controlled “living” polymerization of AEMA was carried out directly in aqueous buffer using 4‐cyanopentanoic acid dithiobenzoate (CTP) as the chain transfer agent (CTA), and 2,2′‐azobis(2‐imidazolinylpropane) dihydrochloride (VA‐044) as the initiator at 50 °C. The controlled “living” character of the polymerization was verified with pseudo‐first order kinetic plots, a linear increase of the molecular weight with conversion, and low polydispersities (PDIs) (<1.2). In addition, well‐defined copolymers of poly(AEMA‐b‐HPMA) have been prepared through chain extension of poly(AEMA) macroCTA with N‐(2‐hydroxypropyl)methacrylamide (HPMA) in water. It is shown that the macroCTA can be extended in a controlled fashion resulting in near monodisperse block copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5405–5415, 2009     

Dispersion RAFT polymerization of 4‐vinylpyridine in toluene mediated with the macro‐RAFT agent of polystyrene dithiobenzoate: Effect of the macro‐RAFT agent chain length and growth of the block copolymer nano‐objects

The dispersion reversible addition‐fragmentation chain transfer (RAFT) polymerization of 4‐vinylpyridine in toluene in the presence of the polystyrene dithiobenzoate (PS‐CTA) macro‐RAFT agent with different chain length is discussed. The RAFT polymerization undergoes an initial slow homogeneous polymerization and a subsequent fast heterogeneous one. The RAFT polymerization rate is dependent on the PS‐CTA chain length, and short PS‐CTA generally leads to fast RAFT polymerization. The dispersion RAFT polymerization induces the self‐assembly of the in situ synthesized polystyrene‐b‐poly(4‐vinylpyridine) block copolymer into highly concentrated block copolymer nano‐objects. The PS‐CTA chain length exerts great influence on the particle nucleation and the size and morphology of the block copolymer nano‐objects. It is found, short PS‐CTA leads to fast particle nucleation and tends to produce large‐sized vesicles or large‐compound micelles, and long PS‐CTA leads to formation of small‐sized nanospheres. Comparison between the polymerization‐induced self‐assembly and self‐assembly of block copolymer in the block‐selective solvent is made, and the great difference between the two methods is demonstrated. The present study is anticipated to be useful to reveal the chain extension and the particle growth of block copolymer during the RAFT polymerization under dispersion condition. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Polymerization‐induced self‐assembly of block copolymer through dispersion RAFT polymerization in ionic liquid

Polymerization‐induced self‐assembly of block copolymer through dispersion RAFT polymerization has been demonstrated to be a valid method to prepare block copolymer nano‐objects. However, volatile solvents are generally involved in this preparation. Herein, the in situ synthesis of block copolymer nano‐objects of poly(ethylene glycol)‐block‐polystyrene (PEG‐b‐PS) in the ionic liquid of 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIN][PF₆]) through the macro‐RAFT agent mediated dispersion polymerization is investigated. It is found that the dispersion RAFT polymerization of styrene in the ionic liquid of [BMIN][PF₆] runs faster than that in the alcoholic solvent, and the dispersion RAFT polymerization in the ionic liquid affords good control over the molecular weight and the molecular weight distribution of the PEG‐b‐PS diblock copolymer. The morphology of the in situ synthesized PEG‐b‐PS diblock copolymer nano‐objects, e.g., nanospheres and vesicles, in the ionic liquid is dependent on the polymerization degree of the solvophobic block and the concentration of the fed monomer, which is somewhat similar to those in alcoholic solvent. It is anticipated that the dispersion RAFT polymerization in ionic liquid broads a new way to prepare block copolymer nano‐objects. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1517–1525     

R‐RAFT approach for the polymerization of N‐isopropylacrylamide with a star poly(ε‐caprolactone) core

Reversible addition‐fragmentation chain transfer (RAFT) polymerization is a more robust and versatile approach than other living free radical polymerization methods, providing a reactive thiocarbonylthio end group. A series of well‐defined star diblock [poly(ε‐caprolactone)‐b‐poly(N‐isopropylacrylamide)]₄ (SPCLNIP) copolymers were synthesized by R‐RAFT polymerization of N‐isopropylacrylamide (NIPAAm) using [PCL‐DDAT]₄ (SPCL‐DDAT) as a star macro‐RAFT agent (DDAT: S‐1‐dodecyl‐S′‐(α, α′‐dimethyl‐α″‐acetic acid) trithiocarbonate). The R‐RAFT polymerization showed a controlled/“living” character, proceeding with pseudo‐first‐order kinetics. All these star polymers with different molecular weights exhibited narrow molecular weight distributions of less than 1.2. The effect of polymerization temperature and molecular weight of the star macro‐RAFT agent on the polymerization kinetics of NIPAAm monomers was also addressed. Hardly any radical–radical coupling by‐products were detected, while linear side products were kept to a minimum by careful control over polymerization conditions. The trithiocarbonate groups were transferred to polymer chain ends by R‐RAFT polymerization, providing potential possibility of further modification by thiocarbonylthio chemistry. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Construction of PIB‐b‐PDEAEMA well‐defined amphiphilic diblock copolymers via sequential living carbocationic and RAFT polymerization

A series of well‐defined amphiphilic diblock copolymers consisting of hydrophobic polyisobutylene (PIB) and hydrophilic poly(2‐(diethylamino)ethyl methacrylate) (PDEAEMA) segments was synthesized via the combination of living carbocationic polymerization and reversible addition fragmentation chain transfer (RAFT) polymerization. Living carbocationic polymerization of isobutylene followed by end‐capping with 1,3‐butadiene was first performed at ?70 °C to give a well‐defined allyl‐Cl‐terminated PIB with a low polydispersity (M_w/M_n =1.29). This end‐functionalized PIB was further converted to a macromolecular chain transfer agent for mediating RAFT block copolymerization of 2‐(diethylamino)ethyl methacrylate at 60 °C in tetrahydrofuran to afford the target well‐defined PIB‐b‐PDEAEMA diblock copolymers with narrow molecular weight distributions (M_w/M_n ≤1.22). The self‐assembly behavior of these amphiphilic diblock copolymers in aqueous media was investigated by fluorescence spectroscopy and transmission electron microscope, and furthermore, their pH‐responsive behavior was studied by UV‐vis and dynamic light scattering. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1478–1486     

Kinetic investigation of the RAFT polymerization of p‐acetoxystyrene

The kinetics of the RAFT polymerization of p‐acetoxystyrene using a trithiocarbonate chain transfer agent, S‐1‐dodecyl‐S′‐(α,α′‐dimethyl‐α″‐acetic acid)trithiocarbonate, DDMAT, was investigated. Parameters including temperature, percentage initiator, concentration, monomer‐to‐chain transfer agent ratio, and solvent were varied and their impact on the rate of polymerization and quality of the final polymer examined. Linear kinetic plots, linear increase of M_n with monomer conversion, and low final molecular weight dispersities were used as criteria for the selection of optimized polymerization conditions, which included a temperature of 70 or 80 °C with 10 mol % AIBN initiator in bulk for low conversions or in 1,4‐dioxane at a monomer‐to‐solvent volume ratio of 1:1 for higher conversions This study opens the way for the use of DDMAT as a chain transfer agent for RAFT polymerization to incorporate p‐acetoxystyrene together with other functional monomers into well‐defined copolymers, block copolymers, and nanostructures. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2517–2524, 2010     

Facile synthesis of star‐shaped copolymers via combination of RAFT and ring opening polymerization

Reversible addition fragmentation chain transfer (RAFT) polymerization and bifunctional sparteine/thiourea organocatalyst‐mediated ring opening polymerization (ROP) were combined to produce poly(L ‐lactide) star polymers and poly(L ‐lactide‐co‐styrene) miktoarm star copolymers architecture following a facile experimental procedure, and without the need for specialist equipment. RAFT was used to copolymerize ethyl acrylate (EA) and hydroxyethyl acrylate (HEA) into poly(EA‐co‐HEA) co‐oligomers of degree of polymerization 10 with 2, 3, and 4 units of HEA, which were in turn used as multifunctional initiators for the ROP of L ‐lactide, using a bifunctional thiourea organocatalytic system. Furthermore, taking advantage of the living nature of RAFT polymerization, the multifunctional initiators were chain extended with styrene (poly((EA‐co‐HEA)‐b‐styrene) copolymers), and used as initiators for the ROP of L ‐lactide, to yield miktoarm star copolymers. The ROP reactions were allowed to proceed to high conversions (>95%) with good control over molecular weights (ca. 28,000‐230,000 g/mol) and polymer structures being observed, although the molecular weight distributions are generally broader (1.3–1.9) than those normally observed for ROP reactions. The orthogonality of both polymerization techniques, coupled with the ubiquity of HEA, which is used as a monomer for RAFT polymerization and as an initiator for ROP, offer a versatile approach to star‐shaped copolymers. Furthermore, this approach offers a practical approach to the synthesis of polylactide star polymers without a glove box or stringent reaction conditions. The phase separation properties of the miktoarm star copolymers were demonstrated via thermal analyses. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6396–6408, 2009     

Block copolymers of dodecafluoroheptyl methacrylate and butyl methacrylate by RAFT miniemulsion polymerization

Reversible addition‐fragmentation chain transfer (RAFT) miniemulsion polymerization of butyl methacrylate (BMA) and dodecafluoroheptyl methacrylate (DFMA) was carried out with 2‐cyanoprop‐2‐yl dithiobenzoate (CPDB) as chain transfer agent (CTA). Concentration effects of RAFT agent and initiator on kinetics and molecular weight were investigated. No obvious red oil layer (phase's separation) and coagulation was observed in the first stage of homopolymerization of BMA. The polymer molecular weights increased linearly with the monomer conversion with polydispersities lower than 1.2. At 75 °C, the monomer conversion could achieve above 96% in 3 h with [momomer]:[RAFT]:[KPS] = 620:4:1 (mole ratio). The results showed excellent controlled/living polymerization characteristics and a very fast polymerization rate. Furthermore, the synthesis of poly(BMA‐b‐DFMA) diblock copolymers with a regular structure (PDI < 1.30, PMMA calibration) was performed by adding the monomer of DFMA at the end of the RAFT miniemulsion polymerization of BMA. The success of diblock copolymerization was showed by the molecular weight curves shifting toward higher molar mass, recorded by gel permeation chromatography before and after block copolymerization. Compositions of block copolymers were further confirmed by ¹H NMR, FTIR, and DSC analysis. The copolymers exhibited a phase‐separated morphology and possessed distinct glass transition temperatures associated with fluoropolymer PDFMA and PBMA domains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1585–1594, 2007     

Synthesis of amphiphilic and thermosensitive graft copolymers with fluorescence P(St‐co‐(p‐CMS))‐g‐PNIPAAM by combination of NMP and RAFT methods

A three‐step process, combining nitroxide‐mediated polymerization (NMP) and reversible addition‐fragmentation chain transfer (RAFT) polymerization techniques, for synthesizing well‐defined amphiphilic and thermosensitive graft copolymers with fluorescence poly(styrene‐co‐(p‐chloromethylstyrene))‐g‐poly(N‐isopropylacrylamide) (P(St‐co‐(p‐CMS))‐g‐PNIPAAM), was conducted. Firstly, the NMP of styrene (St) and p‐chloromethylstyrene (p‐CMS) were carried out using benzoyl peroxide (BPO) as the initiator to obtain the random copolymers of P(St‐co‐(p‐CMS)). Secondly, the random copolymers were converted into macro‐RAFT agents with fluorescent carbazole as Z‐group through a simple method. Then the macro‐RAFT agents were used in the RAFT polymerization of N‐isopropylacrylamide (NIPAAM) to prepare fluorescent amphiphilic graft copolymers P(St‐co‐(p‐CMS))‐g‐PNIPAAM with controlled molecular weights and well‐defined structures. The copolymers obtained were characterized by gel permeation chromatography (GPC), ¹H nuclear magnetic resonance (NMR) spectroscopy, and FT‐IR spectroscopy. The size of self‐assembly micelles of the resulting graft copolymers in deionized water was studied by high performance particle sizer (HPPS), the results showed that the Z‐average size of the micelles increased with the increase of molecular weights of PNIPAAM in side chains. The aqueous solution of the micelles prepared from P(St‐co‐(p‐CMS))‐g‐PNIPAAM using a dialysis method showed a lower critical solution temperature (LCST) at ～ 27.5 °C, which was below the value of NIPAAM homopolymer (32 °C). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5318–5328, 2007     

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     

Facile synthesis of dumbbell‐shaped dendritic‐linear‐dendritic triblock copolymer via reversible addition‐fragmentation chain transfer polymerization

We report the first instance of facile synthesis of dumbbell‐shaped dendritic‐linear‐dendritic triblock copolymer, [G‐3]‐PNIPAM‐[G‐3], consisting of third generation poly(benzyl ether) monodendrons ([G‐3]) and linear poly(N‐isopropylacrylamide) (PNIPAM), via reversible addition‐fragmentation chain transfer (RAFT) polymerization. The key step was the preparation of novel [G‐3]‐based RAFT agent, [G‐3]‐CH₂SCSSCH₂‐[G‐3] (1), from third‐generation dendritic poly(benzyl ether) bromide, [G‐3]‐CH₂Br. Due to the bulky nature of [G‐3]‐CH₂Br, its transformation into trithiocarbonate 1 cannot go to completion, a mixture containing ～80 mol % of 1 and 20 mol % [G‐3]‐CH₂Br was obtained. Dumbbell‐shaped [G‐3]‐PNIPAM₃₁₀‐[G‐3] triblock copolymer was then successfully obtained by the RAFT polymerization of N‐isopropylacylamide (NIPAM) using 1 as the mediating agent, and trace amount of unreacted [G‐3]‐CH₂Br was conveniently removed during purification by precipitating the polymer into diethyl ether. The dendritic‐linear‐dendritic triblock structure was further confirmed by aminolysis, and fully characterized by gel permeation chromatography (GPC) and ¹H‐NMR. The amphiphilic dumbbell‐shaped triblock copolymer contains a thermoresponsive PNIPAM middle block, in aqueous solution it self‐assembles into spherical nanoparticles with the core consisting of hydrophobic [G‐3] dendritic block and stabilized by the PNIPAM central block, forming loops surrounding the insoluble core. The micellar properties of [G‐3]‐PNIPAM₃₁₀‐[G‐3] were then fully characterized. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1432–1445, 2007     

Reversible addition–fragmentation chain transfer polymerization of 2‐naphthyl acrylate with 2‐cyanoprop‐2‐yl 1‐dithionaphthalate as a chain‐transfer agent

The reversible addition–fragmentation chain transfer (RAFT) polymerizations of 2‐naphthyl acrylate (2NA) initiated by 2,2′‐azobisisobutyronitrile were investigated with 2‐cyanoprop‐2‐yl 1‐dithionaphthalate (CPDN) as a RAFT agent at various temperatures in a benzene solution. The results of the polymerizations showed that 2NA could be polymerized in a controlled way by RAFT polymerization with CPDN as a RAFT agent; the polymerization rate was first‐order with respect to the monomer concentration, and the molecular weight increased linearly with the monomer conversion. The polydispersities of the polymer were relatively low up to high conversions in all cases. The chain‐extension reactions of poly(2‐naphthyl acrylate) (P2NA) with methyl methacrylate and styrene successfully yielded poly(2‐naphthyl acrylate)‐b‐poly(methyl methacrylate) and poly(2‐naphthyl acrylate)‐b‐polystyrene block polymers, respectively, with narrow polydispersities. The P2NA obtained by RAFT polymerization had a strong ultraviolet absorption at 270 nm, and the molecular weights had no apparent effect on the ultraviolet absorption intensities; however, the fluorescence intensity of P2NA increased as the molecular weight increased and was higher than that of 2NA. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2632–2642, 2005     

Synthesis of ω‐sulfonated polystyrene via reversible addition fragmentation chain transfer polymerization and postpolymerization modification

The synthesis of chain‐end sulfonated polystyrene [PS (ω‐sulfonated PS)] by reversible addition fragmentation chain transfer (RAFT) polymerization followed by postpolymerization modification was investigated by two methods. In the first method, the polymer was converted to a thiol‐terminated polymer by aminolysis. This polymer was then sulfonated by oxidation of the thiol end‐group with m‐chloroperoxybenzoic acid (m‐CPBA) to produce a sulfonic acid end‐group. In the second method, the RAFT‐polymerized polymer was directly sulfonated by oxidation with m‐CPBA. After purification by column chromatography, ω‐sulfonated PS was obtained by both methods with greater than 95% end‐group functionality as measured by titration. The sulfonic acid end‐group could be neutralized with various ammonium or imidazolium counter ions through acid–base or ionic metathesis reactions. The effect of the ionic end‐groups on the glass transition temperature of the PS was found to be consistent with what is known for PS ionomers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Controlled polymerization of 2‐(diethylamino)ethyl methacrylate and its block copolymer with N‐isopropylacrylamide by RAFT polymerization

Poly(2‐(diethylamino)ethyl methacrylate) (PDEAEMA) homopolymers with low polydispersities were synthesized by reversible addition fragmentation chain transfer (RAFT) radical polymerization. The performances of two chain transfer agents, 2‐cyanoprop‐2‐yl dithiobenzoate and 4‐cyanopentanic acid dithiobenzoate (CPADB), were compared. It was found that the polymerization of 2‐(diethylamino) ethyl methylacrylate was under good control in the presence of CPADB with 4,4′‐azobis(4‐cyanopentanoic acid) (ACPA) as initiator in 1,4‐dioxane at 70 °C. The kinetic behaviors were investigated under different CPADB/ACPA molar ratios. A long polymerization inhibition period was observed at high [CPADB]/[ACPA] ratio. The influences of [CPADB]/[ACPA] ratio, monomer/[CPADB] ratio, and temperature were studied with respect to monomer conversion, molecular weight control, and polydispersity index (PDI). The PDI decreased from 1.21 to 1.12, as the CPADB/ACPA molar ratio changed from 2 to 10. The molecular weight of PDEAEMA could be controlled by monomer/CPADB molar ratio. The control over MW and PDI was improved as the temperature increased from 60 to 70 °C; however, an additional increase to 80 °C led to a loss of control. Using PDEAEMA macroRAFT agent, pH/thermo double‐responsive block copolymers of PDEAEMA and poly(N‐isopropylacrylamide) (PDEAEMA‐b‐PNIPAM) with narrow polydispersity (PDI, 1.24) were synthesized. The lower critical solution temperature of PDEAEMA‐b‐PNIPAM block copolymer depended on the environmental pH. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3294–3305, 2008     

Synthesis and characterization of hyperbranched amphiphilic block copolymers prepared via self‐condensing RAFT polymerization

Four families of hyperbranched amphiphilic block copolymers of styrene (Sty, less polar monomer) and 2‐vinylpyridine (2VPy, one of the two more polar monomers) or 4‐vinylpyridine (4VPy, the other polar monomer) were prepared via self‐condensing vinyl reversible addition‐fragmentation chain transfer polymerization (SCVP‐RAFT). Two families contained 4VPy as the more polar monomer, one of which possessing a Sty‐b‐4VPy architecture, and the other possessing the reverse block architecture. The other two families bore 2VPy as the more polar monomer and had either a 2VPy‐b‐Sty or a Sty‐b‐2VPy architecture. Characterization of the hyperbranched block copolymers in terms of their molecular weights and compositions indicated better control when the VPy monomers were polymerized first. Control over the molecular weights of the hyperbranched copolymers was also confirmed with the aminolysis of the dithioester moiety at the branching points to produce linear polymers with number‐average molecular weights slightly greater than the theoretically expected ones, due to recombination of the resulting thiol‐terminated linear polymers. The amphiphilicity of the hyperbranched copolymers led to their self‐assembly in selective solvents, which was probed using atomic force microscopy and dynamic light scattering, which indicated the formation of large spherical micelles of uniform diameter. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1310–1319     

Long‐lived intermediates in reversible addition–fragmentation chain‐transfer (RAFT) polymerization generated by γ radiation

A novel experimental procedure is presented that allowed probing of reversible addition–fragmentation chain‐transfer (RAFT) free‐radical polymerizations for long‐lived species. The new experimental sequence consisted of gamma irradiation of a mixture of initial RAFT agent (cumyl dithiobenzoate) and monomer at ambient temperature, a subsequent predetermined waiting period without initiation source also at ambient temperature, and then heating of the reaction mixture to a significantly higher temperature. After each sequence step, the monomer conversion and molecular weight distribution were determined, indicating that controlled polymer formation occurs only during the heating period. The results indicated that stable intermediates (either radical or nonradical in nature) are present in such experiments because thermal self‐initiation of the monomer can be excluded as the reason for polymer formation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1058–1063, 2002     

One‐pot synthesis of hyperbranched glycopolymers by RAFT polymerization

Soluble hyperbranched glycopolymers were prepared by copolymerization of glycan monomers with reversible addition‐fragmentation chain transfer polymerization (RAFT) inimers in a simple one‐pot reaction. Two novel RAFT inimers, 2‐(methacryloyloxy)ethyl 4‐cyano‐4‐(phenylcarbonothioylthio)pentanoate (MAE‐CPP) and 2‐(3‐(benzylthiocarbonothioylthio)propanoyloxy)ethyl acrylate (BCP‐EA) were synthesized and used to prepare hyperbranched glycopolymers. Two types of galactose‐based saccharide monomers, 6‐O‐methacryloyl‐1,2:3,4‐di‐O‐isopropylidene‐D ‐galactopyranose (proGal‐M) and 6‐O‐(2′‐acrylamido‐2′‐methylpropanoate)‐1,2:3,4‐di‐O‐isopropylidene‐D ‐galactopyranose (proGal‐A), containing a methacrylate and an acrylamide group, respectively, were also synthesized and polymerized under the mediation of the MAE‐CPP and BCP‐EA inimers, respectively. In addition, hyperbranched poly(proGal‐M), linear poly(proGal‐A), and hyperbranched poly(proGal‐A) were generated and their polymerization kinetics were studied and compared. An unexpected difference was observed in the kinetics between the two monomers during polymerization: the relationship between polymerization rate and concentration of inimer was totally opposite in the two monomer–inimer systems. Branching analysis was conducted by using degree of branching (DB) as the measurement parameter. As expected, a higher DB occurred with increased inimer content. Furthermore, these polymers were readily deprotected by hydrolysis in trifluoroacetic acid solution resulting in water‐soluble polymers. The resulting branched glycopolymers have potential as biomimetics of polysaccharides. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of well‐designed polymers carrying saccharide moieties via RAFT miniemulsion polymerization

Two hydrophobic vinyl saccharide monomers based on D ‐glucose and D ‐fructose were polymerized by employing the reversible addition‐fragmentation transfer (RAFT) miniemulsion polymerization technique to prepare well‐designed glycopolymers. Three dithiobenzoate‐RAFT agents [S?C(Ph)S? R], 1‐phenylethyl dithiobenzoate (PED), 2‐phenylprop‐2‐yl dithiobenzoate (PPD), and 2‐cyanoprop‐2‐yl dithiobenzoate (CPD), were used to control the growth of polymer chains. The best results were obtained in the presence of the PPD‐RAFT agent and the formed polymers have polydispersity index's (PDI) lower than 1.15. Under adequate miniemulsion polymerization conditions, a glycopolymer with PDI of 1.1 and molecular weight of 5 × 10⁴ g/mol has been successfully synthesized in a short reaction time of 100 min. Furthermore, some block copolymers containing saccharide segment with butyl or methyl methacrylate were prepared. Copyright © 2007 John Wiley & Sons, Ltd.