Direct Synthesis of Double Hydrophilic Statistical Di‐ and Triblock Copolymers Comprised of Acrylamide and Acrylic Acid Units via the MADIX Process

Double hydrophilic statistical, diblock and triblock copolymers comprised of acrylamide and acrylic acid units have been synthesized in aqueous medium using the MADIX process. Starting from an either monofunctional or difunctional xanthate, the resulting AB and ABA‐type double hydrophilic block copolymers (DHBC) exhibited molar masses predetermined by the initial monomer/xanthate precursor molar ratio and polydispersity indices in the range 1.2–1.5. Batch copolymerizations yielded well‐defined statistical copolymers that were chain‐extended for the synthesis of novel poly‐ (acrylic acid‐stat‐acrylamide)‐block‐polyacrylamide DHBC.     

Synthesis and self‐assembly of poly(styrene)‐b‐poly(N‐vinylpyrrolidone) amphiphilic diblock copolymers made via a combined ATRP and MADIX approach

Amphiphilic diblock copolymers of polystyrene (PS) and poly(N‐vinylpyrrolidone) (PNVP) were prepared by a combination of ATRP and MADIX. Well‐defined PS with bromine end group was synthesized by ATRP in bulk at 110 °C using (1‐bromoethyl) benzene as an initiator. The Br‐ end group was then converted to xanthate as verified by ¹H NMR spectroscopy, elemental analysis, and UV‐spectroscopy. PS‐b‐PNVP copolymers were produced by MADIX of NVP in bulk at 60 °C using PS‐xanthate as a macro‐chain transfer agent and the kinetics of polymerization were investigated. The structures of PS‐b‐PNVP were characterized using GPC and ¹H NMR. Amphiphilic PS‐b‐PNVP could form spherical micelles with PS cores and PNVP shells in aqueous solution as confirmed by ¹H NMR and laser light scattering (LLS). The values of critical micelle concentration of PS‐b‐PNVP and the average aggregation number of PS‐b‐PNVP in the micelles were measured using pyrene as a probe and static LLS, respectively. The aggregation number increases concomitantly with temperature (10–50 °C), but the hydrodynamic radius of the micelles remains almost constant over the same temperature range, which may indicate shell dehydration at a higher temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5604–5615, 2008     

Influence of sodium dodecyl sulfate on the kinetics and control of RAFT/MADIX polymerization of acrylamide

Aqueous radical polymerizations of acrylamide were conducted in the presence of varying concentrations of sodium dodecyl sulfate (SDS) and two xanthate reversible addition‐fragmentation chain transfer (RAFT) agents: the small, hydrophobic Rhodixan A1 and the oligomeric, amphiphilic PAm₇‐XA1. The presence of SDS led to significant retardation of the polymerization, while the apparent activity of both RAFT/MADIX agents decreased as the SDS concentration increased. PAm₇‐XA1 was affected to a lesser degree than Rhodixan A1, probably due to its lesser tendency to become sequestered in SDS micelles. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 760–765     

Synthesis of amphiphilic poly(methyl methacrylate‐ b‐ethylene oxide) copolymers from monohydroxy telechelic poly(methyl methacrylate) as macroinitiator

The synthesis of well‐defined poly(methyl methacrylate)‐block‐poly(ethylene oxide) (PMMA‐b‐PEO) dibock copolymer through anionic polymerization using monohydroxy telechelic PMMA as macroinitiator is described. Living anionic polymerization of methyl methacrylate was performed using initiators derived from the adduct of diphenylethylene and a suitable alkyllithium, either of which contains a hydroxyl group protected with tert‐butyldimethylsilyl moiety in tetrahydrofuran (THF) at ?78 °C in the presence of LiClO₄. The synthesized telechelic PMMAs had good control of molecular weight with narrow molecular weight distribution (MWD). The ¹H NMR and MALDI‐TOF MS analysis confirmed quantitative functionalization of chain‐ends. Block copolymerization of ethylene oxide was carried out using the terminal hydroxyl group of PMMA as initiator in the presence of potassium counter ion in THF at 35 °C. The PMMA‐b‐PEO diblock copolymers had moderate control of molecular weight with narrow MWD. The ¹H NMR results confirm the absence of trans‐esterification reaction of propagating PEO anions onto the ester pendants of PMMA. The micellation behavior of PMMA‐b‐PEO diblock copolymer was examined in water using ¹H NMR and dynamic light scattering. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2132–2144, 2008     

Isoprene‐Assisted Radical Coupling of (Co)polymers Prepared by Cobalt‐Mediated Radical Polymerization

Tackling blocks : The isoprene‐assisted radical coupling (I‐ARC) of polymers prepared by cobalt‐mediated radical polymerization (see picture) is the first efficient radical coupling method that is not restricted to short chains. When applied to AB diblock copolymers, I‐ARC constitutes a straightforward approach to the preparation of novel symmetrical ABA triblock copolymers.

     

Synthesis and Characterization of Poly(N-isopropylacrylamide) and Poly(vinyl acetate) Diblock Copolymers via MADIX Process

The synthesis of diblock copolymers of poly(N-isopropylacrylamide) (PNIPAM) and poly(vinyl acetate) (PVAc) was performed by macromolecular design via interchange of xanthates (MADIX) process. Following the preparation of methyl (isopropoxycarbonothioyl) sulfanyl acetate (MIPCTSA) as chain transfer agent, it was reacted with vinyl acetate to obtain PVAc macro-chain transfer agent. Then, block copolymerization was completed by successive addition of N-isopropylacrylamide (NIPAM). ¹H NMR spectroscopy confirmed the presence of both blocks in the copolymer structure, with the expected composition based on the feed ratio. Size Exclusion Chromatography (SEC) was used to investigate the relative values of molecular characteristics. Only 20% of PVAc was converted to block copolymer. The resultant block copolymer structures were further examined in terms of their morphologies as well as critical micelle concentration (CMC) by using ESEM and Fluorescence Excitation Spectroscopic techniques, respectively. Morphological characterization confirmed amphiphilic block copolymer formation with the existence of mainly ca. 100 nm well distributed micelles. The thermo responsive amphiphilic behavior of the block copolymer solutions were followed by Dynamic Light Scattering (DLS) technique.     

Synthesis of comb‐shaped poly(methyl methacrylate)‐b‐poly(polytetrahydrofuran acrylate) under 60Co γ‐ray irradiation

Comb‐shaped graft copolymers with poly(methyl methacrylate) as a handle were synthesized by the macromonomer technique in two steps. First, polytetrahydrofuran acrylate (A‐PTHF), prepared by the living cationic ring‐opening polymerization of tetrahydrofuran, underwent homopolymerization with 1‐(ethoxycarbonyl)prop‐1‐yl dithiobenzoate as an initiator under ⁶⁰Co γ irradiation at room temperature; Second, the handle of the comb‐shaped copolymers was prepared by the block copolymerization of methyl methacrylate with P(A‐PTHF) as a macroinitiator under ⁶⁰Co γ irradiation. The two‐step polymerizations were proved to be controlled with the following evidence: the straight line of ln[M]₀/[M] versus the polymerization time, the linear increase in the number‐average molecular weight with the conversion, and the relatively narrow molecular weight distribution. The structures of the P(A‐PTHF) and final comb‐shaped copolymers were characterized by ¹H NMR spectroscopy and gel permeation chromatography. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3367–3378, 2002     

Xanthates as Chain‐Transfer Agents in Controlled Radical Polymerization (MADIX): Structural Effect of the O‐Alkyl Group

The capability of three chain‐transfer agents, O‐alkyl‐S‐(1‐ethoxycarbonyl)ethyl xanthates (CH₃CHCO₂C₂H₅)S(CS)OZ′, to control the free‐radical polymerization of styrene and ethyl acrylate by the MADIX process was examined. The reactivity of the xanthates varied according to the following trend: Z′  CH₂CH₃ < CH₂CF₃ < CH[P(O)(OEt)₂]CF₃. This change in reactivity allowed a lowering of the polydispersity index from 2.0 for Z′  CH₂CH₃ to 1.15 for Z′  CH[P(O)(OEt)₂]CF₃ in the case of the polymerization of styrene.

Evolution of M _w/M _n with conversion during the polymerization of ethyl acrylate in the presence of xanthates X₁ , X₂ and X₃ . Reaction conditions: [EA]₀ = 4.6 M , [X]₀ = 5.75 × 10⁻² M , [AIBN]₀ = 1.72 × 10⁻³ M ; T = 80 °C ; solvent: toluene.     

Synthesis of AB diblock copolymers by atom-transfer radical polymerization (ATRP) and living polymerization of alpha-amino acid-N-carboxyanhydrides

The synthesis of poly(methyl acrylate)-block-poly(gamma-benzyl-L-glutamate) (PMA-b-PBLG) diblock copolymers, using atom-transfer radical polymerization (ATRP) of methyl acrylate and living polymerization of gamma-benzyl-L-glutamate-N-carboxyanhydride (Glu-NCA) is described. Amido-amidate nickelacycle end groups were incorporated onto amino-terminated poly(methyl acrylates), and the resulting complexes were successfully used as macroinitiators for the growth of polypeptide segments. This method allows the controlled preparation of polypeptide-block-poly(methyl acrylate) diblock architectures with control over polypeptide chain length and without the formation of homopolypeptide contaminants.     

Synthesis of poly(benzyl glutamate‐b‐styrene) rod‐coil block copolymers by dual initiation in one pot

We have developed a metal free synthetic pathway to homopolypeptide rod‐coil block copolymers. The concept was proven for the synthesis of poly(benzyl‐L ‐glutamate‐b‐styrene). A dual initiator containing a primary amine and a nitroxide group was used in a macroinitiation approach with high initiation efficiency. Good control over the molecular weight in the ring opening polymerization of benzyl‐L ‐glutamate N‐carboxyanhydride was obtained in DMF at 0 °C yielding poly(benzyl‐L ‐glutamates) with low polydispersities around 1.1. The almost quantitative incorporation of the dual initiator was confirmed by MALDI‐ToF analysis. Macroinitiation of styrene by nitroxide‐mediated controlled radical polymerization yielded the block copolymer with high structural control. The diblock structure was confirmed by molecular weight increase upon macroinitiation by size exclusion chromatography and retention time comparison with homopolymers using gradient polymer elution chromatography. Both polymerizations were also successfully conducted in one pot without intermediate isolation owing to the high compatibility of both polymerization techniques. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3068–3077, 2008     

Synthesis of Seven-Arm Poly(vinyl pyrrolidone) Star Polymers with Lysozyme Core Prepared by MADIX/RAFT Polymerization

A poly(vinyl pyrrolidone) (PVP) seven-arms star polymer with lysozyme core was synthesized by conjugating linear N-succinimidyl ester terminated PVP polymer to lysozyme. Reactive PVP polymers were synthesized using a MADIX/RAFT agent functionalized with N-succinimidyl ester. The polymerization of N-vinyl pyrrolidone proceeded in a living fashion up to more than 90% conversion reaching molecular weight of up to 33 000 g · mol⁻¹ with narrow molecular weight distributions. The PVP polymer was conjugated to lysozyme resulting in the attachment of seven PVP polymers to one lysozyme core. While the reaction was found to be complete when using low-molecular weight PVP, some by-products with less than seven arms were observed when using PVP with a molecular weight of 33 000 g · mol⁻¹.

     

Synthesis of polystyrene–poly(tert‐butyl methacrylate)–poly(ethylene oxide) triarm star block copolymers

Three alternative routes, using the heterobifunctional macroinitiator technique, have been developed to obtain polystyrene–poly(tert‐butyl methacrylate)–poly(ethylene oxide) triarm star block copolymers. Only the route showing the reverse initiation of tert‐butyl methacrylate on potassium alkoxide leads to the pure star, whereas the other strategies lead to incomplete initiation because of either an increase in the side reactions, such as transesterification, or a decrease in the accessibility toward bulky catalysts. These limits are linked to the particular location of the initiating group at the junction of the two blocks of the copolymer precursor. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1745–1751, 2004     

Synthesis and characterization of ABA-type block copolymer of poly(trimethylene carbonate) with poly(ethylene glycol): Bioerodible copolymer

ABA-type block copolymers of poly(trimethylene carbonate) with poly(ethylene glycol) (M_n 6820), PTMC-b-PEG-b-PTMC, were synthesized by the ring-opening polymerization of 1,3-dioxan-2-one (trimethylene carbonate) in the presence of poly-(ethylene glycol) with stannous octoate catalyst, and the copolymers with various compositions were obtained. The PTMC-b-PEG-b-PTMC copolymers were characterized with Fourier transform infrared and nuclear magnetic resonance spectroscopies. The intrinsic viscosities of resulting copolymers increased with the increase of 1,3-dioxan-2-one content in feed while the molar ratio of monomer over catalyst kept constant. It has been observed that the glass transition temperature (T_g) of the PTMC segments in copolymers, recorded from differential scanning calorimetry, was dependent on the composition of copolymers. The melting temperature (T_m) of PEG blocks in copolymer was lower than that of PEG polymer, and then disappeared as the length of PTMC blocks increased. The results of dynamic contact angle measurement clearly revealed that the hydrophilicity of resulting copolymers increased greatly with the increase of PEG content in copolymers. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 695–702, 1998     

Synthesis of amphiphilic block copolymer consisting of glycopolymer and poly(l‐lactide) and preparation of sugar‐coated polymer aggregates

The block glycopolymer, poly(2‐(α‐d ‐mannopyranosyloxy)ethyl methacrylate)‐b‐poly(l ‐lactide) (PManEMA‐b‐PLLA), was synthesized via a coupling approach. PLLA having an ethynyl group was successfully synthesized via ring‐opening polymerization using 2‐propyn‐1‐ol as an initiator. The ethynyl functionality of the resulting polymer was confirmed by MALDI‐TOF mass spectroscopy. In contrast, PManEMA having an azide group was prepared via AGET ATRP using 2‐azidopropyl 2‐bromo‐2‐methylpropanoate as an initiator. The azide functionality of the resulting polymer was confirmed by IR spectroscopy. The Cu(I)‐catalyzed 1,3‐dipolar cycloaddition between PLLA and PManEMA was performed to afford PManEMA‐b‐PLLA. The block structure was confirmed by ¹H NMR spectroscopy and size exclusion chromatography. The aggregating properties of the block glycopolymer, PManEMA_16k‐b‐PLLA_6.4k (M _n,PManEMA = 16,000, M _n,PLLA = 6400) was examined by ¹H NMR spectroscopy, fluorometry using pyrene, and dynamic light scattering. The block glycopolymer formed complicated aggregates at concentrations above 21 mg·L^?1 in water. The d ‐mannose presenting property of the aggregates was also characterized by turbidimetric assay using concanavalin A. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 395–403     

Synthesis of complex macromolecules using iterative copper(0)‐mediated radical polymerization

Copper(0) mediated radical polymerization is an efficient and versatile polymerization technique which allows the control of acrylates and methacrylates with an unprecedented maintenance of end group fidelity (～100%) during the polymerization. In this highlight, we summarize recent works using Cu(0)‐mediated radical polymerization for the synthesis of multiblock copolymers via an iterative approach. This approach has been successfully implemented for the synthesis of decablock copolymers, constituted of blocks with a degree of polymerization ranging from 3–4 to 100 units as well as for the preparation of multiblock star polymers. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2083–2098     

Synthesis of poly(chloromethylstyrene‐b‐styrene) block copolymers by controlled free‐radical polymerization

The controlled free‐radical polymerization of styrene and chloromethylstyrene monomers in the presence of 2,2,6,6‐tetramethyl‐1‐piperidinyloxyl (TEMPO) has been studied with the aim of synthesizing block copolymers with well‐defined structures. First, TEMPO‐capped poly(chloromethylstyrene) was prepared. Among several initiating systems [self‐initiation, dicumyl peroxide, and 2,2′‐azobis(isobutyronitrile)], the last offered the best compromise for obtaining a good control of the polymerization and a fast polymerization rate. The rate of the TEMPO‐mediated polymerization of chloromethylstyrene was independent of the initial concentration of TEMPO but unexpectedly higher than the rate of the thermal self‐initiated polymerization of chloromethylstyrene. Transfer reactions to the chloromethyl groups were thought to play an important role in the polymerization kinetics and the polydispersity index of the resulting poly(chloromethylstyrene). Second, this first block was used as a macroinitiator in the polymerization of styrene to obtain the desired poly(chloromethylstyrene‐b‐styrene) block copolymer. The kinetic modeling of the block copolymerization was in good agreement with experimental data. The block copolymers obtained in this work exhibited a low polydispersity index (weight‐average molecular weight/number‐average molecular weight < 1.5) and could be chemically modified with nucleophilic substitution reactions on the benzylic site, opening the way to a great variety of architectures. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3845–3854, 2000     

Controlled (Co)Polymerization of Methacrylates Using a Novel Symmetrical Trithiocarbonate RAFT Agent Bearing Diphenylmethyl Groups

Herein, we report a novel type of symmetrical trithiocarbonate chain transfer agent (CTA) based diphenylmethyl as R groups. The utilization of this CTA in the Reversible Addition-Fragmentation chain Transfer (RAFT) process reveals an efficient control in the polymerization of methacrylic monomers and the preparation of block copolymers. The latter are obtained by the (co)polymerization of styrene or butyl acrylate using a functionalized macro-CTA polymethyl methacrylate (PMMA) previously synthesized. Data show low molecular weight dispersity values (Đ < 1.5) particularly in the polymerization of methacrylic monomers. Considering a typical RAFT mechanism, the leaving groups (R) from the fragmentation of CTA should be able to re-initiate the polymerization (formation of growth chains) allowing an efficient control of the process. Nevertheless, in the case of the polymerization of MMA in the presence of this symmetrical CTA, the polymerization process displays an atypical behavior that requires high [initiator]/[CTA] molar ratios for accessing predictable molecular weights without affecting the Đ. Some evidence suggests that this does not completely behave as a common RAFT agent as it is not completely consumed during the polymerization reaction, and it needs atypical high molar ratios [initiator]/[CTA] to be closer to the predicted molecular weight without affecting the Đ. This work demonstrates that MMA and other methacrylic monomers can be polymerized in a controlled way, and with “living” characteristics, using certain symmetrical trithiocarbonates.     

叠氮聚合物的合成

叠氮基团不仅是高含能基团和高反应性基团,而且也可以被转化为其他官能基团。叠氮聚合物可用作高能黏合剂、交联材料以及表面改性材料等,还可以作为合成功能高分子的前体,因此叠氮聚合物的合成研究引起了高分子科学家的广泛关注。到目前为止,叠氮聚合物的合成方法研究取得了新的进展,主要包括: 高分子化学改性法、环醚类叠氮单体阳离子开环聚合法和不饱和叠氮单体自由基聚合法。本文综述了近些年来叠氮聚合物的合成研究方面取得的主要成果和进展,其中包括本课题组的一些研究工作。     

A Facile Synthesis of Cleavable Block Copolymers via Tandem Polymerizations of NMRP and ATRP

A functionalized compound, 4‐(2‐bromoisobutyryl)‐2,2,6,6‐tetra‐methylpiperidine‐1‐oxyl (Br‐TEMPO), was synthesized and used to synthesize block copolymers through tandem nitroxide‐mediated radical polymerization (NMRP) and atom transfer radical polymerization (ATRP). First, Br‐TEMPO was used to mediate the polymerization of styrene. The kinetics of polymerization proved a typical “living” nature of the reaction and the effectiveness in the mediation of polymerization of Br‐TEMPO. Then the PS‐Br macroinitiator was used to initiate atom transfer radical polymerization (ATRP). A series of acrylates were initiated by PS‐Br macroinitiators in typical ATRP processes at various conditions. The controlled polymerization of ATRP was also confirmed by molecular weight and kinetic analysis. Several cleavable block copolymers of PS‐b‐P(t‐BA), PS‐b‐P(n‐BA), and PS‐b‐PMA, with different molecular weights, were synthesized via this strategy. Relatively low polydispersities (<1.5) were observed and the molecular weights were in agreement with the theoretical ones. Hydrolysis of PS‐b‐P(t‐BA) was carried out, giving amphiphilic block copolymer PS‐b‐PAA without the cleavage of C‐ON bond or ester bond. All the block copolymers have two T_gs as demonstrated by DSC. A typical cleavable block copolymer of PS‐b‐PMA was cleaved by adding phenylhydrazine at 120°C to produce homopolymers in situ.