用双硫酯链转移法合成嵌段聚合物

研究了以双硫酯为链转移剂进行的均聚和嵌段共聚物的合成 .首先合成大分子链转移剂 ,得到分子量可控、多分散性系数较小的均聚物PMMA、PBMA、PEMA、PEA、PBA、PMA、PSt,多分散性系数一般小于 1 30 .在相同的条件下 ,甲基丙烯酸酯类的聚合速度最快 ,苯乙烯其次 ,丙烯酸酯类最慢 .用末端带有双硫酯基团的PSt、PBMA、PBA为链转移剂 ,加入多种第二单体聚合得到实测分子量与理论分子量接近 ,且多分散性系数较小的两嵌段聚合物 .在链转移剂和引发剂的比例为 3∶1～ 6∶1的范围内 ,聚苯乙烯同样可以作为第一嵌段得到和其它酯类单体的两嵌段聚合物 .1 H NMR方法证明了聚合物的末端带有双硫酯基团 .嵌段聚合时必须加入微量的自由基引发剂以形成大分子自由基 ,达到较好的控制聚合效果     

以双硫酯为链转移剂的活性自由基聚合

合成并研究了两种双硫酯链转移剂的纯化方法 ,进行了多种单体以双硫酯为链转移剂的活性自由基聚合及嵌段共聚 .发现以PhC(S)SC(CH3) 2 Ph为链转移剂的效果比PhC(S)SCH(CH3)Ph好 ,聚合产物的多分散性系数较小 .引发剂与链转移剂的摩尔数比为 1∶3 5～ 1∶4 2时 ,得到多分散性系数小 ,实测分子量与理论分子量相近的聚合产物 .聚合物的分子量随时间和转化率的增加而增加 ,加入第二单体形成嵌段共聚物 ,具有活性聚合特征 .聚甲基丙烯酸酯大分子引发剂引发丙烯酸酯单体聚合时 ,聚合速度最快 .     

用大分子引发剂法制备嵌段共聚物

主要介绍了用大分子引发剂法制备嵌段共聚物的方法。大分子引发剂是从已商品化的功能聚合物制得或用其它活性聚合方法合成。从单封端的端羟基聚合物、其它单官能团或双官能团聚合物以及双功能基团缩聚物制得大分子引发剂．然后用于原子转移自由基聚合(ATRP)、氮氧稳定自由基聚合以及可逆加成裂解链转移(RAFT)聚合等．可制得结构可控、分子量分布窄的嵌段共聚物。     

苯乙烯和乙烯基三甲氧基硅烷嵌段共聚物的制备及表征

以苯乙烯(St)为单体,二硫代萘甲酸异丁腈酯(CPDN)为可逆-加成断裂链转移聚合(RAFT)试剂,合成大分子链转移剂,再加入不同质量的乙烯基三甲氧基硅烷(A171),得到嵌段比不同的共聚物P(St-b-A171)。通过核磁共振谱仪1 H-NMR、凝胶渗透色谱GPC、动态力学分析仪DMA和接触角等方法对P(St-b-A171)结构进行了表征。结果表明:随着nSt/nA171嵌段比从1∶0.15增加到1∶0.45,P(St-b-A71)数均分子量从10400增加到14000,PDI指数从1.42增加到1.58;聚合物成膜后接触角由78.4°增加到89.6°。通过以上分析得出结论,RAFT合成嵌段共聚物的嵌段比对P(St-b-A171)性能有较大影响。     

RAFT聚合制备氟硅嵌段共聚物及结构性能

以三硫代酯封端的聚二甲基硅氧烷作为大分子链转移剂,通过可逆加成-断裂链转移聚合(RAFT)制备了一系列聚二甲基硅氧烷-b-聚甲基丙烯酸十二氟庚酯(PDMS-b-PDFHMA)二嵌段共聚物.利用凝胶渗透色谱(GPC)、傅里叶变换红外光谱(FT-IR)、氢核磁共振谱(1H-NMR)对该嵌段共聚物的组成、结构和分子量进行了表...     

ABA型两亲嵌段共聚物的合成及表征

以α ,α′ 二溴代二甲苯为引发剂 ,CuBr/2 ,2′ 联吡啶为催化体系 ,制备了双溴端基的分子量分布窄的聚苯乙烯 (MWD =1 18) .再以此作为大分子引发剂 ,实现了甲基丙烯酸对硝基苯酯的原子转移自由基聚合 ,制得了分子量可控且分子量分布窄的ABA型嵌段共聚物 ,再经水解、酸化 ,得到了聚甲基丙烯酸 b 聚苯乙烯 b 聚甲基丙烯酸ABA型两亲嵌段共聚物     

双响应性嵌段共聚物聚异丙基丙烯酰胺-b-聚(L-谷氨酸)的合成与表征

通过组合可逆加成-断裂链转移自由基聚合(RAFT)和氨基酸可控开环聚合(ROP)两种方法,合成得到聚异丙基丙烯酰胺-b-聚(L-谷氨酸)嵌段共聚物(PNIPAAm55-b-PLGA35).以5-氨基戊醇、12-硫醇等为原料,合成了新型的芴甲氧基保护的三硫酯链转移剂.使用核磁氢谱、凝胶排阻色谱对产物进行验证.并通过紫外-可见分光光度法、透射电镜、动态光散射表征,证明了该嵌段共聚物具有刺激响应性的胶束化行为.     

聚丙烯酸-b-聚丙烯酸甲酯的制备及其在丙烯酸丁酯乳液聚合中的应用

采用三硫代碳酸S-1-十二烷基-S'-(a,a'-二甲基-a″-乙酸)酯(MTTCD)作为链转移剂,偶氮二异丁腈(AIBN)为引发剂,丙烯酸(AA)为第一单体,通过可逆加成-断裂链转移(RAFT)自由基聚合合成大分子链转移剂PAA-MTTCD,以丙烯酸甲酯(MA)为第二单体,合成5种不同嵌段比的两亲性嵌段共聚物聚丙烯酸-b-聚丙烯酸甲酯(PAA-b-PMA)。采用FT IR和1H NMR确定了PAA-MTTCD和PAA-b-PMA的结构,用GPC测定了PAA-MTTCD和PAA-b-PMA的分子量及分子量分布。分析了聚合反应动力学,发现该聚合具有活性可控聚合的特征,聚合动力学呈一级线性关系。测定了PAA-b-PMA的乳化性能,并将其作为乳化剂用于丙烯酸丁酯(BA)的乳液聚合中,同时考察了不同嵌段长度共聚物对乳液聚合的影响。结果表明,具有21个AA单元和18个MA单元的两亲性嵌段共聚物具有较好的乳化性能,其作为乳化剂时乳液聚合效果相对最好。     

聚丙烯酸-b-聚丙烯酸甲酯的制备及其在乳液聚合中的应用

采用三硫代碳酸S-1-十二烷基-S'-(a,a'-二甲基-a"-乙酸)酯(MTTCD)作为链转移剂,偶氮二异丁腈(AIBN)为引发剂,丙烯酸(AA)为第一单体,通过可逆加成-断裂链转移(RAFT)自由基聚合合成大分子链转移剂PAA-MTTCD,以丙烯酸甲酯(MA)为第二单体,合成5种不同嵌段比的两亲性嵌段共聚物聚丙烯酸-b-聚丙烯酸甲酯(PAA-b-PMA).采用FT IR和1H NMR确定了PAA-MTTCD和PAA-b-PMA的结构,用GPC测定了PAA-MTTCD和PAA-b-PMA的分子量及分子量分布.分析了聚合反应动力学,发现该聚合具有活性可控聚合的特征,聚合动力学呈一级线性关系.测定了PAA-b-PMA的乳化性能,并将其作为乳化剂用于丙烯酸丁酯(BA)的乳液聚合中,同时考察了不同嵌段长度共聚物对乳液聚合的影响.结果表明,具有21个AA单元和18个MA单元的两亲性嵌段共聚物具有较好的乳化性能,其作为乳化剂时乳液聚合效果相对最好.     

用多官能链转移剂通过普通自由基聚合制备两亲性杂臂星形聚合物

以偶氮二异丁腈为引发剂,四(3-巯基丙酸季戊四醇四酯)(PETMP)为链转移剂进行甲基丙烯酸甲酯(MMA)的自由基聚合,得到了含有残余巯基的聚甲基丙烯酸甲酯大分子链转移剂(HS-PMMA).然后,以HS-PMMA作为大分子链转移剂进行甲基丙烯酸叔丁酯(tBMA)的自由基聚合,合成了杂臂星形聚合物.最后,将所得杂臂星形聚合物的PtBMA链段水解得到了两亲性杂臂星形聚合物.     

Synthesis and photoresponsive behavior of azobenzene‐containing side‐chain liquid crystalline diblock polymers with polypeptide block

Well‐defined azobenzene‐containing side‐chain liquid crystalline diblock copolymers composed of poly[6‐(4‐methoxy‐azobenzene‐4′‐oxy) hexyl methacrylate] (PMMAZO) and poly(γ‐benzyl‐L ‐glutamate) (PBLG) were synthesized by click reaction from alkyne‐ and azide‐functionalized homopolymers. The alkyne‐terminated PMMAZO homopolymers were synthesized by copper‐mediated atom transfer radical polymerization with a bromine‐containing alkyne bifunctional initiator, and the azido‐terminated PBLG homopolymers were synthesized by ring‐opening polymerization of γ‐benzyl‐L ‐glutamate‐N‐carboxyanhydride in DMF at room temperature using an amine‐containing azide initiator. The thermotropic phase behavior of PMMAZO‐b‐PBLG diblock copolymers in bulk were investigated using differential scanning calorimetry and polarized light microscopy. The PMMAZO‐b‐PBLG diblock copolymers exhibited a smectic phase and a nematic phase when the weight fraction of PMMAZO block was more than 50%. Photoisomerization behavior of PMMAZO‐b‐PBLG diblock copolymers and the corresponding PMMAZO homopolymers in solid film and in solution were investigated using UV–vis. In solution, trans–cis isomerization of diblock copolymers was slower than that of the corresponding PMMAZO homopolymers. These results may provide guidelines for the design of effective photoresponsive anisotropic materials. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

可逆加成-断裂链转移方法合成两亲液晶嵌段功能大分子及其自组装的研究

采用可逆加成-断裂链转移(RAFT)可控聚合反应方法,合成制备了一系列窄分子量分布、结构规整的两亲液晶嵌段功能大分子聚甲基丙烯酸亚己基胆固醇酯-b-聚甲基丙烯酸羟乙酯(PMA6Chol-block-PHEMA).运用核磁共振(NMR)、凝胶渗透色谱仪(GPC)、示差扫描热分析仪(DSC)和热失重分析仪(TGA)对制备所得两亲嵌段功能大分子的化学结构、热物理性能以及液晶相结构与转变温度进行了研究.在此基础上,采用纳米沉淀法研究了所得系列液晶嵌段功能大分子在混合溶剂中的自组装,制备得到微米尺度球形组装体.研究结果表明刚性胆固醇液晶共聚单元的存在对于溶液自组装产生重要影响.     

Reversible addition–fragmentation transfer polymerization of p‐nitrophenyl acrylate and synthesis of diblock copolymers poly(p‐nitrophenyl acrylate)‐b‐polystyrene

Poly(p‐nitrophenyl acrylate)s (PNPAs) with different molecular mass and narrow polydispersity were successfully synthesized for the first time by reversible addition–fragmentation transfer (RAFT) polymerization with azobisisobutyronitrile (AIBN) as an initiator and [1‐(ethoxy carbonyl) prop‐1‐yl dithiobenzoate] as the chain‐transfer agent. Although the molecular mass of PNPAs can be controlled by the molar ratio of NPA to RAFT agent and the conversion, a trace of homo‐PNPA was found, especially at the early stage of polymerization. The dithiobenzoyl‐terminated PNPA obtained was used as a macro chain‐transfer agent in the successive RAFT block copolymerization of styrene (St) with AIBN as the initiator. After purification by two washings with cyclohexane and nitromethane to remove homo‐PSt and homo‐PNPA, the pure diblock copolymers, PNPA‐b‐PSt's, with narrow molecular weight distribution were obtained. The structural analysis of polymerization products by ¹H NMR and GPC verified the formation of diblock copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4862–4872, 2004     

Synthesis of bis(2,2′:6′,2″-terpyridine)-terminated telechelic polymers by RAFT polymerization and ruthenium-polymer complexation thereof

Well-defined polystyrenes and poly(n-butyl acrylate)s of the two ends being functionalized with terpyridine groups were synthesized via addition-fragmentation chain transfer (RAFT) polymerization using a symmetric bisterpyridine-functionalized trithiocarbonate as a chain transfer agent (CTA). Kinetic studies on RAFT mediated thermal polymerization of styrene indicated the controlled polymerization. Corresponding triblock copolymers of styrene and n-butyl acrylate were obtained by utilizing the bisterpyridine-functionalized homopolymers as the macro-CTAs. Supramolecular metallo-polystyrenes with different repeat blocks were prepared by the chelating interaction between the terpyridine ends and Ru(II) ions. The formation of the metallo-polymers was proven by UV-vis spectra and dynamic light scattering (DLS).     

Synthesis of zwitterionic block copolymers via RAFT polymerization

A series of poly [2-(dimethylamino)ethyl methacrylate (DMA)-sodium acrylate (SA)] diblock copolymers were synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymerization exhibits controlled characters: well-controlled molecular weight, narrow molecular weight distribution, molecular weight increasing with polymerization time. The zwitterionic diblock copolymers show rich solution behaviors. Dynamic light scattering (DLS) indicated the formation of micelles and reverse micelles of copolymers is affected by net charge density of copolymers. Microcalorimetry studies showed that the lower critical solution temperature (LCST) increases with incorporation of hydrophilic segments in buffer.     

CMC and Phase Separation Studies of RAFT Mediated Amphiphilic Diblock Glycopolymers with Methyl Acrylate and Styrene

Summary: Interesting new CMC and phase separation data of carbohydrate-based self-assembling core-shell nanoparticles which were synthesized via the Reversible Addition-Fragmentation Transfer (RAFT) process. The macro-RAFT agent, poly(3-O- Methacryloyl-1,2:5,6-di-O-isopropylidene-D-glucofuranose) (PMAlpGlc), was prepared by RAFT polymerization of the glycomonomer with cumyl phenyl dithioacetate as the chain transfer agent. Chain extension with styrene and methyl acrylate afforded the diblock copolymers (PMAlpGlc-b-styrene and PMAlpGlc-b-methyl acrylate) having predetermined molecular weight and narrow molecular weight distributions. Acidolysis of these diblock copolymers were undertaken and confirmed by NMR. Core-shell nanoparticles were observed by TEM.     

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     

Photocrosslinkable liquid‐crystalline block copolymers with coumarin units synthesized with atom transfer radical polymerization

A new class of liquid‐crystalline (LC) homopolymers of poly{11‐[4‐(3‐ethoxycarbonyl‐coumarin‐7‐oxy)‐carbonylphenyloxy]‐undecyl methacrylate} containing a coumarin moiety as a photocrosslinkable unit with various polymerization degrees and their LC‐coil diblock and LC‐coil‐LC triblock copolymers with polystyrene as the coil segment was synthesized with the atom transfer radical polymerization method. All the homopolymers and block copolymers synthesized here exhibited narrow polydispersities, indicating well‐controlled living polymerization. Differential scanning calorimetry, polarized optical microscopy, and wide‐angle X‐ray diffraction confirmed that all the homopolymers and block copolymers exhibit a monolayer smectic A phase. Coumarin moieties in the polymers can be photodimerized under λ > 300 nm light irradiation to yield crosslinked network structures, which improve the thermal stability of a polymer nanostructure because of microphase separation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2197–2206, 2003     

Synthesis and characterization of well‐defined diblock and triblock copolymers of poly(N‐isopropylacrylamide) and poly(ethylene oxide)

Well‐defined diblock and triblock copolymers composed of poly(N‐isopropylacrylamide) (PNIPAM) and poly(ethylene oxide) (PEO) were successfully synthesized through the reversible addition–fragmentation chain transfer polymerization of N‐isopropylacrylamide (NIPAM) with PEO capped with one or two dithiobenzoyl groups as a macrotransfer agent. ¹H NMR, Fourier transform infrared, and gel permeation chromatography instruments were used to characterize the block copolymers obtained. The results showed that the diblock and triblock copolymers had well‐defined structures and narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight < 1.2), and the molecular weight of the PNIPAM block in the diblock and triblock copolymers could be controlled by the initial molar ratio of NIPAM to dithiobenzoate‐terminated PEO and the NIPAM conversion. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4873–4881, 2004