PCL-b-PNAGA嵌段共聚物的制备及表征

聚己内酯(PCL)是一种性能优良的生物相容性及降解性良好生物材料,在生物医药方面有着巨大的潜能,但其具有很强的疏水性。本文利用N-丙烯酰基甘氨酰胺(NAGA)的亲水性通过可逆加成-断裂链转移聚合(RAFT)制备嵌段共聚物PCL-b-PNAGA,并通过FI-IR和1H-NMR表征证明了各个产物的成功制备。结果表明:成功制备了单体NAGA,大分子链转移剂PCL-CTA和嵌段共聚物PCL-b-PNAGA。     

嵌段共聚物PBA-b-PDMAEA的合成及其分散性能研究

利用可逆加成断裂链转移自由基聚合(RAFT)的方法制备了AB型嵌段共聚物PBA-b-PDMAEA,用红外光谱(FT-IR)、核磁氢谱(1HNMR)和凝胶渗透色谱(GPC)等方法对其结构进行了表征。以PBA-b-PDMAEA为分散剂,分别制备了PBK7、PG7、PB15:3、PR101、PR112、PR254、PY42、PY74和PY154等色浆,利用激光粒度仪(LSPSA)和透射电镜(TEM)对色浆的粒度进行了测定,结果表明PBA-b-PDMAEA作为分散剂,性能优异且通用性好,对于炭黑、无机颜料和有机颜料都适用。     

两亲嵌段共聚物PIBOA-b-PAA的制备及其共混改性EVA胶黏剂的研究

聚丙烯(PP)、聚乙烯(PE)等非极性聚合物材料广泛地应用在各个领域,应用过程中总会遇到不同程度的粘接问题,所以对其表面进行改善是非常有必要的。本文首先合成了链转移剂TRIT,然后通过可逆加成-断裂链转移(RAFT)自由基聚合反应制备出以丙烯酸异冰片酯(IBOA)为第一单体、丙烯酸(AA)为第二单体的两亲性嵌段共聚物PIBOA-b-AA,再将其与EVA胶粘剂共混,以改善EVA胶黏剂在非极性聚合材料表面的润湿性能以及附着力性能。结果发现:共混两亲PIBOA-b-PAA嵌段共聚物能够有效地提高EVA胶黏剂在PP板、PE板上的粘结力、粘结强度和剪切模量,同时当添加的两亲PIBOA-b-PAA嵌段共聚物占总质量的7%,效果最优异。     

偏氯乙烯活性自由基聚合及其嵌段共聚物合成研究进展

偏氯乙烯(VDC)是重要含氯单体之一,通过活性自由基聚合可以制备分子量可控、分子量分布窄的VDC聚合物,并可进一步制备VDC嵌段共聚物,提高VDC聚合物的性能、拓展其应用。本文对VDC活性自由基聚合(主要是可逆加成-断裂链转移聚合)及其嵌段共聚物合成研究进行了综述。     

双亲嵌段共聚物PSt-b-P(St-alt-MA)-b-PAA的自组装行为

以三硫代碳酸二(α, α'-二甲基-α-乙酸)酯(BDATC)为链转移剂, 以苯乙烯、马来酸酐、丙烯酸为原料, 通过可逆加成-断裂链转移(RAFT)合成了双亲嵌段共聚物PSt-b-P(St-alt-MA)-b-PAA。通过选择性溶剂N, N-二甲基甲酰胺(DMF)诱导聚合物进行自组装, 利用紫外-可见光光度仪、纳米激光粒度仪详细研究了共聚物中亲疏水嵌段长度、初始浓度、体系pH值对聚合物自组装行为的影响。通过化学交联的方法制备得到了聚合物交联胶束, 利用透射电镜表征了形貌与尺寸, 研究明确了其形状和尺寸的稳定性。结果表明, 上述因素均会影响共聚物的自组装行为和自组装胶束的形态, 经乙二胺交联得到的交联自组装胶束平均粒径为145.4nm, 并具有良好的形状和尺寸稳定性。     

RAFT方法合成两亲性嵌段共聚物的研究进展

可逆加成一断裂链转移(RAFT)聚合是制备嵌段共聚物的重要方法之一,介绍了队RAFT聚合方法的基本原理及其所用的RAFT链转移剂基础上,综述了国内外利用RAFT聚合方法合成两亲性嵌段共聚物的研究现状.     

三嵌段离子液体共聚物P2VP(Bu)TFSI-b-PS-b-P(POEGMA)合成与表征

在链转移剂S-十二烷基-S′-(α,α′-二甲基-α″-乙酸)-三硫代碳酸酯的调控下,偶氮二异丁腈引发单体2-乙烯基吡啶、苯乙烯和聚乙二醇单甲醚甲基丙烯酸酯连续聚合,制备了含有聚2-乙烯基吡啶(P2VP)、聚苯乙烯(PS)和聚(聚乙二醇单甲醚甲基丙烯酸酯)[P(POEGMA)]链段的三嵌段共聚物P2VP105-b-PS...     

三嵌段离子液体共聚物mPEG-b-PS-b-PVBMImTFSI合成及表征

通过可逆加成断裂链转移自由基聚合(RAFT)法,以偶氮二异丁腈为引发剂,合成了含有聚乙二醇单甲醚(mPEG)、聚苯乙烯(PS)和聚对氯甲基苯乙烯(PVBC)链段的三嵌段共聚物mPEG-b-PS-b-PVBC.将合成的共聚物与1-甲基咪唑(NMIm)进行季铵化反应,再与双三氟甲基磺酰亚胺锂(LiTFSI)进行阴离子交换,...     

环境响应性两亲嵌段共聚物的自组装及其药物控释研究进展

两亲嵌段共聚物形成的胶束、囊泡等典型的自组装体可作为纳米医药载体,用于药物的控释,其研究已成为当前胶化、医药和生物学科交叉领域的热点。尤其是聚乙二醇型两亲嵌段共聚物,不仅具有良好的生物相容性,而且通过适当的分子设计可形成对环境具有刺激响应的纳米载体。本文着重综述了这类两亲嵌段共聚物的自组装及其在药物控释方面的研究,总结了影响自组装的因素,并介绍了控释药物的机理。     

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)。     

气溶胶固定剂PAM-b-PVTES的合成及表征

以S,S-二苄基三硫代碳酸酯(DBTTC)为链转移剂，丙烯酰胺(AM)为第一单体，乙烯基三乙氧基硅烷(VTES)为第二单体，通过RAFT聚合制备了两亲嵌段共聚物，其水溶液可作为一种气溶胶固定剂用于涉核环境下放射性气溶胶的去除。通过FTIR、1H NMR、DSC、GPC对聚合物分子结构与性能进行了表征。通过黏度表征结果表明：随着链转剂用量的减少，黏度增加。表面张力和接触角测试结果表明：随着VTES的引入，表面张力降低到40.44 mN/m；接触角降低到11.9°；通过气溶胶沉降固定实验表明：对PTI-A2粉尘的沉降固定效率为91.04%。预期在涉核环境下作为放射性气溶胶沉降固定剂可得到应用。     

Double Stimuli-Responsive di- and Triblock Copolymers of Poly(N-isopropylacrylamide) and Poly(1-vinylimidazole): Synthesis and Self-Assembly

For the first time, double stimuli-responsive properties of poly(N-isopropylacrylamide) (PNIPA) and poly(1-vinylimidazole) (PVIM) block copolymers in aqueous solutions were studied. The synthesis of PNIPA₆₀-b-PVIM₉₀ and PNIPA₂₈-b-PVIM₆₂-b-PNIPA₂₉ was performed using reversible addition–fragmentation chain transfer (RAFT) polymerization. The polymers were characterized by size exclusion chromatography and ¹H NMR spectroscopy. The conformational behavior of the polymers was studied using dynamic light scattering (DLS) and fluorescence spectroscopy (FS). It was found that PNIPA and block copolymers conformation and ability for self-assembly in aqueous medium below and above cloud point temperature depend on the locus of hydrophobic groups derived from the RAFT agent within the chain. Additionally, the length of PVIM block, its locus in the chain and charge perform an important role in the stabilization of macromolecular micelles and aggregates below and above cloud point temperature. At 25 °C the average hydrodynamic radius (R_h) of the block copolymer particles at pH 3 is lower than at pH 9 implying the self-assembling of macromolecules in the latter case. Cloud points of PNIPA₆₀-b-PVIM₉₀ are ~43 °C and ~37 °C at a pH of 3 and 9 and of PNIPA₂₈-b-PVIM₆₂-b-PNIPA₂₉ they are ~35 °C and 31 °C at a pH of 3 and 9. Around cloud point independently of pH, the R_h value for triblock copolymer rises sharply, achieves the maximum value, then falls and reaches the constant value, while for diblock copolymer, it steadily grows after reaching cloud point. The information about polarity of microenvironment around polymer obtained by FS accords with DLS data.     

Study on controlled free‐radical polymerization in the presence of dithiobenzoic acid (DTBA)

Polymerizations of methylacrylate, styrene and methyl methacrylate were carried out in the presence dithiobenzoic acid (DTBA). The results exhibit controlled polymerization characters: well‐controlled molecular weight, narrow molecular weight distribution (minimal value: 1.08), molecular weight linearly increasing with conversion and first‐order kinetics of polymerization. The polymers were characterized by ¹H NMR and GPC. The effect of temperature and molar ratio DTBA/AIBN on polymerization was investigated. A mechanism is proposed to explain the controlled polymerization characters. © 2000 Society of Chemical Industry     

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     

One‐step synthesis of triarm block copolymers via simultaneous reversible‐addition fragmentation chain transfer and ring‐opening polymerization

One‐step synthesis of star copolymers by reversible addition–fragmentation chain transfer (RAFT) and ring‐opening polymerization (ROP) by using a novel dual initiator is reported. Triarm block copolymers comprising one polystyrene (or polyacrylamide) arm and two poly(β‐butyrolactone) arms were synthesized in one‐step by simultaneous RAFT polymerization of styrene (St) (or acrylamide, designated as AAm) and ROP of β‐butyrolactone (BL) in the presence of a novel trifunctional initiator, 1,2‐propanediol ethyl xanthogenate (RAFT‐ROP agent). This dual initiator was obtained through the reaction of 3‐chloro‐1,2‐propanediol with the potassium salt of ethyl xanthogenate. The principal parameters such as monomer concentration, initiator concentration, and polymerization time that affect the one‐step polymerization reaction were evaluated. The characterization of the products was achieved using Fourier‐transform infrared spectroscopy (FTIR), ¹H‐nuclear magnetic resonance (¹H‐NMR), ¹³C‐nuclear magnetic resonance (¹³C‐NMR), Gas chromatography–mass spectrometry (GC–MS), gel‐permeation chromatography (GPC), thermogravimetric analysis (TGA), and fractional precipitation (γ) techniques. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Kinetics of RAFT emulsion polymerization of styrene mediated by oligo(acrylic acid‐b‐styrene) trithiocarbonate

The kinetics of ab initio reversible addition‐fragmentation chain transfer (RAFT) emulsion polymerization of styrene using oligo(acrylic acid‐b‐styrene) trithiocarbonate as both polymerization mediator and surfactant were systematically investigated. The initiator concentration was set much lower than that in the conventional emulsion polymerization to significantly suppress the irreversible termination reaction. It was found that decreased rapidly but the nucleation efficiency of micelles increased with the decrease of the initiator concentrations due to the significant radical exit. The particle number ( ) did not follow the classic Smith–Eward equation but was proportional to [I]^?0.4[S]^0.7. It was suggested that RAFT emulsion polymerization could be fast enough for commercial use even at extremely low initiator concentrations and low macro‐RAFT agent concentrations due to the higher particle nucleation efficiency at lower initiator concentration. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2126–2134, 2016     

RAFT synthesis of poly(N‐isopropylacrylamide) and poly(methacrylic acid) homopolymers and block copolymers: Kinetics and characterization

Reversible addition‐fragmentation chain transfer (RAFT) polymerization was used successfully to synthesize temperature‐responsive poly(N‐isopropylacrylamide) (PNIPAAm), poly(methacrylic acid) (PMAA), and their temperature‐responsive block copolymers. Detailed RAFT polymerization kinetics of the homopolymers was studied. PNIPAAm and PMAA homopolymerization showed living characteristics that include a linear relationship between M _n and conversion, controlled molecular weights, and relatively narrow molecular weight distribution (PDI < 1.3). Furthermore, the homopolymers can be reactivated to produce block copolymers. The RAFT agent, carboxymethyl dithiobenzoate (CMDB), proved to control molecular weight and PDI. As the RAFT agent concentration increases, molecular weight and PDI decreased. However, CMDB showed evidence of having a relatively low chain transfer constant as well as degradation during polymerization. Solution of the block copolymers in phosphate buffered saline displayed temperature reversible characteristics at a lower critical solution temperature (LCST) transition of 31°C. A 5 wt % solution of the block copolymers form thermoreversible gels by a self‐assembly mechanism above the LCST. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1191–1201, 2006