通过RAFT聚合制备经GMA偶联的PMMA/TiO2杂化纳米复合物

利用表面修饰法合成了常用单体甲基丙烯酸缩水甘油酯(GMA)修饰的TiO2纳米粒子。以甲基丙烯酸甲酯(MMA)为单体,S-1-十二烷基-S′-(α,α′-二甲基-α″-乙酸)三硫代碳酸酯(DDACT)为RAFT试剂,在纳米TiO2表面进行可逆加成-断裂链转移(RAFT)接枝聚合,PMMA"经表面接枝到(grafting through)"改性后的纳米TiO2表面。结果表明,随聚合时间的增加,纳米TiO2表面接枝聚合物PMMA的量增加,颗粒的团聚得到明显减缓。     

PNIPAM改性纤维素球调控布洛芬释放

简要介绍了聚(N-异丙基丙烯酰胺)(PNIPAM)改性的纤维素球对药物的可控释放,该产物具有温度敏感和p H值敏感的特性。运用可逆加成-断裂链转移聚合反应,将PNIPAM链接到纤维素微球上,分别采用傅里叶变换红外光谱,扫描电子显微镜,透射电子显微镜,X射线光子能谱分析和热重分析等方法,证实了PNIPAM成功地链接到纤维素微球上。PNIPAM-纤维素微球的直径为1.2~2μm,具有良好的生物相容性,有利于用作药物载体控制药物释放。布洛芬被选择作为模型药物分子以测试PNIPAM-纤维素微球的药物负载和释放性能。结果表明,PNIPAM-纤维素球的布洛芬释放速度在25℃比在38℃快,在p H值7.4快于p H值4.0。由于PNIPAM-纤维素微球的热敏性和p H值敏感性,使得它可以广泛应用于可控的药物释放。     

RAFT合成pH和温度响应的双亲水嵌段共聚物

以S-十二烷基-S-′(2-羧基-异丙基)三硫酯(DDATC)为链转移剂,偶氮二异丁腈(AIBN)为引发剂,通过可逆加成-断裂链转移(RAFT)聚合合成了结构明确,窄相对分子质量分布(Mw/Mn=1.27)的聚(N-异丙基丙烯酰胺)-b-聚(N,N-二甲氨基甲基丙烯酸乙酯)(PNIPAm-b-PDMAEMA)双亲水两嵌段共聚物。共聚物的结构通过红外光谱、核磁共振氢谱和凝胶渗透色谱表征。采用透光率法、稳态荧光光谱法、电位滴定和动态光散射考察了PNIPAm-b-PDMAEMA在水中对温度和pH敏感的胶束化行为。结果表明,PNIPAm-b-PDMAEMA具有温度响应性,其水溶液的低临界溶液温度(LCST)为32.3℃,溶液温度高于LCST后发生温度诱导的胶束化,胶束的流体力学半径(Rh)为50 nm左右,Rh随温度升高而稍微增大;PNIPAm-b-PDMAEMA水溶液表现出明显的pH敏感性,25℃时两嵌段共聚物pH诱导胶束化的临界pH=9.8,溶液pH高于临界pH后发生pH诱导的胶束化,胶束的Rh约为31 nm(pH=11.0)。     

SiO2/聚丙烯酰胺类杂化材料的合成研究进展

介绍了SiO2／聚丙烯酰胺类杂化材料的各种制备方法,并对SiO2／聚丙烯酰胺类杂化材料的研究作了展望。     

基于点击化学和可逆加成-断裂链转移自由基聚合合成极性链接枝聚丁二烯

以1-硫代甘油作为改性剂、聚丁二烯为主链,通过热引发和光引发合成了侧基含有羟基的聚丁二烯,以S-1-十二烷基-S′（α-α′-二甲基-α′′乙酸）-三硫代碳酸酯作为可逆加成-断裂链转移自由基聚合试剂、偶氮二异丁腈为引发剂,合成了端羧基聚N,N-二甲基丙烯酰胺,然后将两种官能化的聚合物进行酯化反应制得聚N,N-二甲基丙烯酰胺接枝聚丁二烯。结果表明,采用光引发可以显著提高点击化学的反应效率。用核磁共振氢谱证实了产物含羟基聚丁二烯和端羧基聚N,N-二甲基丙烯酰胺以及接枝聚合物的结构,并显示通过这种方法所制备接枝聚合物的接枝链数目和长度均可控。     

PGMA-b-PS二嵌段共聚物的RAFT/细乳液合成及表征

以2-(十二烷基三硫代碳酸酯)-2-甲基丙烯酸为链转移剂,利用RAFT/细乳液联合技术合成了相对分子质量分布较窄(PDI=1.53)的大分子链转移剂聚甲基丙烯酸缩水甘油酯。再以该大分子为可逆加成-断裂链转移(RAFT)试剂,通过连续加料的方式加入苯乙烯后进一步引发聚合,得到PGMA-b-PS二嵌段共聚物。采用GPC、FT-IR、1H-NMR、DSC等方法对聚合产物进行了表征。结果表明:合成的聚合物为线型二嵌段共聚物,相对分子质量分布为1.87,该聚合过程具有活性/可控特征。DSC测得二嵌段共聚物具有2个玻璃化转变温度(Tg),分别为77.33℃和98.30℃。此外,还考察了单体加料顺序对聚合过程的影响。     

含纳米金聚乙烯基吡咯烷酮/聚(N-异丙基丙烯酰胺)智能杂化微凝胶的合成

以无皂乳液聚合法合成了聚乙烯基吡咯烷酮(PVP).首先,选用乙烯基吡咯烷酮(NVP)作为单体,交联剂与引发剂分别选用了二甲基丙烯酸乙二醇酯(EGDMA)和偶氮二异丁脒盐酸盐(V50),成功合成出PVP种子.再将PVP种子与氯金酸溶液(HAuCl4)混合形成载金微凝胶.最后在合成PVP/PNIPAM载金杂化微凝胶的步骤中...     

自交联法合成相转变温度范围窄的聚(N-异丙基丙烯酰胺)水凝胶微球

在不使用交联剂的情况下,采用无皂乳液聚合法合成自交联聚(N-异丙基丙烯酰胺)(PNIPAM)水凝胶微球。固体13C NMR分析结果表明,PNIPAM水凝胶微球中存在因链转移反应形成的自交联点。自交联PNIPAM水凝胶微球的相转变温度范围很窄,接近非连续体积相转变行为。合成过程中反应温度、反应时间、引发剂用量对微球粒径和溶胀比有比较明显的影响,这些因素对微球的相转变温度及其范围的影响均很小。     

单分散PSt/SiO_2杂化材料微球的制备及表征

以硅酸乙酯和丙烯酸反应制备了硅酸乙酯-丙烯酸单体,再将其和苯乙烯通过无皂乳液法共聚制备了单分散PSt/SiO2杂化材料微球。用FTIR、SEM、EDS、TG-DSC等对杂化材料微球进行了表征。结果表明有机组分和无机组分间以Si-O-C键相连接成交联结构,杂化材料只有一个玻璃化转变温度120℃,杂化材料微球粒径均一、大小约为300nm,单分散性的杂化材料微球乳液在室温下蒸发很容易自组装成有序的结构。     

PNIPAM/锂藻土纳米复合凝胶微球的制备及其弹性力学性能

利用微流控技术,以锂藻土作为交联剂,成功制备得到温度响应型聚（N-异丙基丙烯酰胺）（PNIPAM）与锂藻土的纳米复合凝胶微球,并利用一种简单的微步进单轴压缩装置,分别在25℃和37℃下对具有不同锂藻土含量的PNIPAM/锂藻土纳米复合凝胶微球的弹性力学性能进行系统研究。该微步进单轴压缩装置主要包括三个部分：一个程控进样器用以实现对凝胶微球的微步进压缩,一套配有高分辨率数码相机的侧视光学系统用以记录凝胶微球受压时发生的形变,一台精密电子天平作为力传感器用来记录凝胶微球在特定形变下所受的外力。研究结果表明,纳米复合凝胶微球在25℃和37℃下的形变量H与所受压力F的实验数据与Hertz弹性接触理论方程呈现良好的拟合关系,证明了PNIPAM/锂藻土纳米复合凝胶微球在25℃和37℃下均具有弹性形变行为。同时,随着锂藻土含量的增加,PNIPAM/锂藻土纳米复合凝胶微球的温敏性降低,但其杨氏模量增大。具有相同锂藻土含量的纳米复合凝胶微球,由于温度升高凝胶体积收缩、凝胶结构变得致密,因此在37℃下的杨氏模量大于其在25℃下的杨氏模量。研究结果可为PNIPAM/锂藻土纳米复合凝胶微球的设计与实际应用提供指导。     

Synthesis of novel random and block copolymers of tert-butyldimethylsilyl methacrylate and methyl methacrylate by RAFT polymerization

Hydrophobic-hydrolysable copolymers consisting of methyl methacrylate (MMA) and tert-butyldimethylsilyl methacrylate (TBDMSMA) have been synthesized for the first time by Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization technique using cumyl dithiobenzoate (CDB) and cyanoisopropyl dithiobenzoate (CPDB) as chain transfer agents (CTAs). The monomer reactivity ratios for TBDMSMA (r₁ = 1.40 ± 0.03) and MMA (r₂ = 1.08 ± 0.03) have been determined using a non-linear least-squares fitting method. Well-defined random copolymers PMMA-co-PTBDMSMA have been prepared. Then, the versatility of the RAFT process to synthesize silylated block copolymers with controlled molecular weights and low polydispersities has been demonstrated using two strategies: the synthesis of PMMA-SC(S)Ph or PTBDMSMA-SC(S)Ph as macro-chain transfer agent (macro-CTA) for use in a two step method or an one-pot method which consists in the successive addition of the two monomers. Diblock copolymers with narrow molecular weight distributions (PDI < 1.2) were obtained from the one-pot method with number-average molecular weight values within the range 10,000-22,000 g mol⁻¹.     

Synthesis and nucleation mechanism of inverse emulsion polymerization of acrylamide by RAFT polymerization: A comparative study

Well-defined poly (acrylamide) is synthesized by RAFT inverse emulsion polymerization using hydrophilic and lipophilic initiators. The kinetic behavior observed for RAFT inverse emulsion polymerization is similar to that for RAFT inverse miniemulsion polymerization. The nucleation mechanism of inverse emulsion polymerization of acrylamide is firstly investigated by RAFT polymerization and verified by GPC and SEM measurements. Droplet nucleation is found to be the primary mechanism in the inverse emulsion polymerization of acrylamide. However, polymerization occurring in the continuous phase is not negligible when lipophilic initiator is used.     

Synthesis of thermoresponsive block and graft copolymers via the combination of living cationic polymerization and RAFT polymerization using a vinyl ether-type RAFT agent

A novel vinyl ether-type RAFT agent, benzyl 2-(vinyloxy)ethyl carbonotrithioate (BVCT) was synthesized for various block copolymers via the combination of living cationic polymerization of vinyl ethers and reversible addition−fragmentation chain transfer (RAFT) polymerization. The novel BVCT–trifluoroacetic acid adduct play an important role to produce well-defined block copolymers, which is both as a cationogen under EtAlCl₂ initiation system in the presence of ethyl acetate for living cationic polymerization and a RAFT agent for blocks by RAFT polymerization. The resulting polymer, poly(vinyl ether)s, by living cationic polymerization had a high number average α-end functionality (≥0.9) as determined by both ¹H NMR and MALDI-TOF-MS spectrometry. In addition, this poly(vinyl ether)s worked well as a macromolecular chain transfer agent for RAFT polymerization. The RAFT polymerization of radically polymerizable monomers was conducted in toluene using 2,2′-azobis(isobutyronitrile) at 70 °C. For example, a double thermoresponsive block copolymer (MOVE₆₁-b-NIPAM₁₅₀) consisting of 2-methoxyethyl vinyl ether (MOVE) and N-isopropylacrylamide (NIPAM) was prepared via the combination of living cationic polymerization and RAFT polymerization. The block copolymer reversibly formed and deformed micellar assemblies above the phase separation temperature (T_ps) of poly(NIPAM) block in water. This BVCT is not only functioned as an initiator, but also acted as a monomer. When BVCT was copolymerized with MOVE by living cationic polymerization, followed by graft copolymerization with NIPAM via RAFT polymerization, well-defined graft copolymers (MOVE_n-co-BVCT_m)-g-NIPAM_x (n = 62–73, m = 1–9, x = 19–214) were successfully obtained. However, no micelle formed in water above T_ps of poly(NIPAM) graft chain unlike the case of block copolymers.     

Living free radical polymerization (RAFT) of dodecyl acrylate: Chain length dependent termination, mid-chain radicals and monomer reaction order

The reversible addition fragmentation chain transfer-chain length dependent-termination (RAFT-CLD-T) methodology was employed to map chain length dependent termination rate coefficient, , in dodecyl acrylate (DA) free radical polymerization at 60 and 80 °C. The chain length of the propagating DA radicals was controlled by the RAFT agents methoxycarbonylethyl phenyldithioacetate (MCEPDA) and dimethoxycarbonylethyl trithiocarbonate (DMCETC). In addition, the reaction order of the polymerization process with respect to the monomer concentration was determined at both temperatures and found to be close to 1.55 (60 °C) and 1.75 (80 °C), commensurate with the increased presence of mid-chain radicals. A modeling study demonstrates that the obtained data for the reaction order can be transferred to RAFT polymerization systems. The RAFT-CLD-T procedure was modified to account for the determined reaction orders. The obtained chain length dependence of k_t in dodecyl acrylate polymerizations is in good agreement with the composite model for chain length dependent termination, showing two distinct regions: For the initial chain-length regime up to a degree of polymerization of 20, k_t decreases rapidly with α (in the expression ) being close to 1.15 at 80 °C. At chain lengths exceeding 20, the decrease is significantly less pronounced (α close to 0.22 at 80 °C). At 60 °C, the chain length dependence in both regions is somewhat more pronounced. The RAFT agent DMCETC may not be as suited to map out CLD k_t values in the DA system, since it induces some limited rate retardation effects.     

Synthesis and characterization of azobenzene-functionalized poly(styrene)-b-poly(vinyl acetate) via the combination of RAFT and “click” chemistry

Here, we described a strategy for preparing well-defined block copolymers, poly(styrene)-b-poly(vinyl acetate) (PS-b-PVAc), containing middle azobenzene moiety via the combination of the reversible addition-fragmentation chain transfer (RAFT) polymerization and “click” chemistry. Firstly, a novel RAFT agent containing α-alkyne and azobenzene chromophore in R group, 2-(3-ethynylphenylazophenoxycarbonyl)prop-2-yl-9H-carbazole-9-carbodithioate (EACDT), was synthesized and used to mediate the RAFT polymerization of styrene (St). Well-defined α-alkyne end-functionalized poly(styrene) (PS) was obtained. Secondly, the RAFT polymerization of vinyl acetate (VAc) was conducted using functionalized RAFT reagent with ω-azide structure in Z group, O-(2-azidoethyl) S-benzyl dithiocarbonate (AEBDC). Well-defined ω-azide end-functionalized poly(vinyl acetate) (PVAc) was obtained. Afterwards, the resulting α-alkyne terminated PS was coupled by “click” chemistry with the azide terminated PVAc. The block copolymer, PS-b-PVAc, was obtained with tailored structures. The products from each step were characterized and confirmed by GPC, ¹H NMR, IR and differential scanning calorimetry (DSC) examination. Kinetics of the trans-cis-trans isomerization from azobenzene chromophore in PS-b-PVAc and PS were investigated in CHCl₃ solutions.     

Synthesis of polydimethylsiloxane‐containing block copolymers via reversible addition fragmentation chain transfer (RAFT) polymerization

Low polydispersity polydimethylsiloxane (PDMS) was end functionalized with a reversible addition fragmentation chain transfer (RAFT) agent by the esterification of hydroxyl terminated PDMS with a carboxylic acid functional RAFT agent. These PDMS‐RAFT agents were able to control the free radical polymerization of styrene and substituted styrene monomers to produce PDMS‐containing block copolymers with low polydispersities and targeted molecular weights. A thin film of polydimethylsiloxane‐block‐polystyrene was prepared by spin coating and exhibited a microphase separated morphology from scanning force microscopy measurements. Controlled swelling of these films in solvent vapor produced morphologies with significant long‐range order. This synthetic route will allow the straightforward production of PDMS‐containing block copolymer libraries that will be useful for investigating their thin film morphological behavior, which has applications in the templating of nanostructured materials.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of reaction parameters on the synthesis of hyperbranched polymers via reversible addition fragmentation chain transfer (RAFT) polymerization

The synthesis of hyperbranched poly(methyl methacrylate) (PMMA) via reversible addition fragmentation chain transfer (RAFT) polymerization was investigated by varying the ratio chain transfer agent (CTA): monomer (methyl methacrylate, MMA): brancher (ethylene glycol dimethyl methacrylate, EGDMA): free radical initiator (AIBN) at various temperatures (50, 55, 60, 65, 70 °C). The rate of polymerization was observed to increase with temperature and concentration in brancher, whilst it was lowered by an increase in chain transfer agent concentration. The molecular weight of the samples increased with the ratios brancher: CTA and monomer: CTA. The polydispersity of the samples increase with conversion, as the level of branching increases. At fixed concentration in brancher, an increase of CTA concentration led to polymers with lower PDI. The variation of enthalpy and entropy relative to the monomer reaction were calculated, and it was observed that an increase in the brancher concentration induced an increase in both and , whilst lower CTA concentrations led to an increase in . The variation in Gibbs energy for the monomer reaction was calculated at 60 °C, and results confirmed the presence of a retardation effect when increasing CTA concentration generally observed in RAFT polymerization.     

RAFT polymerization of styrene mediated by naphthalene-containing RAFT agents and optical properties of the polymers

In this paper, we designed and synthesized five novel reversible addition–fragmentation chain transfer (RAFT) agents bearing naphthyl moieties in the Z or R groups, including 3,4,5-trimethoxy-benzyl dithio-2-naphthalenoate (TOBDN), 4-nitrobenzyl dithio-2-naphthalenoate (NBDN), 1-menaphthyl 4-cyanodithiobenzoate (NCDB), 1-menaphthyl dithiobenzoate (NDB) and 1-menaphthyl dithio-2-naphthalenoate (NDN). The RAFT polymerizations of styrene mediated by these RAFT agents with AIBN as the initiator at 80 °C were conducted and evaluated. Except for NCDB, the RAFT agents showed good control over the polymerization at different RAFT agent concentrations: the M_n,GPC increased linearly with the monomer conversion, and the PDIs of the polymers were relatively low (PDI = 1.20–1.50). The structure of RAFT agents bearing three different R groups with naphthyl as the Z group showed less effects on the polymerization rate, while those bearing different Z groups with 1-menaphthyl as the R group presented significant effects on the polymerization rates. The polymerization rate with phenyl as the Z group was higher than that with 2-naphthyl as the Z group, and it decreased significantly when using 4-cycno phenyl as the Z group. Retardation effects were observed with all the RAFT agents. ¹H NMR spectra and chain extension results confirmed that most of the polymer chains were “living”. Ultraviolet (UV) absorption of naphthyl moieties at the R group showed blue shifts compared with those of naphthyl at the Z group. The UV absorption intensity of PS was uniformly lower than that of the corresponding RAFT agent, while the fluorescence intensity of PS was higher than that of the corresponding RAFT agent.     

Synthesis of Gemini‐Like Methyl Acrylate‐Acrylic Acid‐Methyl Acrylate Triblock Copolymers Surfactants by RAFT Polymerization in Solution and Investigation of their Behavior at the Air–Water Interface

A series of methyl acrylate‐acrylic acid amphiphilic triblock copolymers (PMA‐PAA‐PMA) were prepared by solution polymerization using S,S′‐bis (α,α‐dimethy1acetic acid) trithiocarbonate (BDAT) as a reversible addition fragmentation chain transfer (RAFT) agent and methyl acrylate (MA) as the first monomer. The triblock copolymers and their common MA homopolymer precursors were characterized in terms of their compositions, molecular weights and behavior at the air–water interface using ¹H‐NMR spectroscopy, thermogravimetric analysis, gel permeation chromatography, surface tension, transmission electron microscopy (TEM) and dynamic light scattering respectively. The results indicated that PMA‐PAA‐PMA was successfully synthesized through RAFT polymerization. The polydispersity index (PDI) decreased when the molar ratio [n(MA)/n(AA)] increased, the lowest PDI was obtained at 5.23 wt% RAFT and the molecular weights were consistent with the theoretical value as the RAFT agent percentage varied. The polymer neutralized by sodium hydroxide solution shows a low critical micelle concentration (CMC), which was <10^?2 mol L^?1 in water. The A_min values increased and showed a maximum with decreased AA chain length. TEM showed that the neutralized polymer formed a special vesicle structure with large pore structure which led to a low CMC and surface tension of water.