两亲性三嵌段共聚物PAA-PHB-PAA的合成及表征

本文用ATRP方法, 以两端溴化的聚β-羟基丁酸酯链段(Br-PHB-Br)作为大分子引发剂, 丙烯酸叔丁酯为单体, 合成了一种新的三嵌段共聚物聚丙烯酸叔丁酯-聚β-羟基丁酸酯-聚丙烯酸叔丁酯(PtBA-PHB-PtBA). 在酸性条件下进一步水解, 得到了一种两亲性的聚丙烯酸-聚β-羟基丁酸酯-聚丙烯酸(PAA-PHB-PAA)三嵌段共聚物.     

ATRP合成大分子单体法制备核壳结构微球

以α-溴代丙酸乙酯(EPN-Br)为引发剂, N,N, N′,N″,N″-五甲基二亚乙基三胺(PMDETA)为配体,使甲基丙烯酸叔丁酯进行原子转移自由基聚合,合成了端基带溴原子的聚甲基丙烯酸叔丁酯(PtBMA-Br)大分子中间体,通过其与甲基丙烯酸的亲核取代反应,得到了末端C=C双键含量高的大分子单体（MAA-PtBMA）,其相对分子质量可控制在5400-12000g/mol的范围内,分子量分布≤1.20。以偶氮二异丁腈为自由基引发剂,在乙醇中使MAA-PtBMA大分子单体与苯乙烯（St）进行分散共聚,制得了甲基丙烯酸叔丁酯接枝聚苯乙烯（PtBMA-g-PSt）微米级共聚微球,该微球具有核壳结构。     

含偶氮苯两亲性ABA三嵌段共聚物合成与自组装研究

利用原子转移自由基聚合(ATRP)制备了中间链段含对氰基偶氮苯尾挂液晶基元的PMAA-b-PMAZOCN-b-PMAA两亲性三嵌段共聚物.首先合成了含有偶氮苯液晶基元的甲基丙烯酸酯单体;再使用小分子双端引发剂,以对壬基联二吡啶、溴化亚铜为催化剂,通过ATRP反应制备了含偶氮苯液晶侧基的双端大分子引发剂.进一步以氯化亚铜为催化剂,用该大分子引发剂引发甲基丙烯酸叔丁酯聚合,制备了结构规则的PtBMA-b-PMAZOCN-PtBMA三嵌段共聚物.通过在三氟乙酸作用下的选择性水解,将PtBMA段中的甲基丙烯酸叔丁酯单体单元转化为甲基丙烯酸,得到了两端亲水,中间疏水的两亲性ABA三嵌段共聚物.用1H-NMR、GPC、PLM、DSC等对产物进行了表征.并利用溶剂诱导微相分离的方法,研究了该共聚物在THF/水混合溶剂中的自组装行为.TEM结果显示,在采用的亲疏水链段比例的条件下,得到了囊泡结构.囊泡结构的平均直径在300~500 nm.在固态下经过紫外光照射,囊泡结构转变为实心胶体球.     

新型引发剂引发苯乙烯聚合的动力学

采用过氧化2-乙基己基碳酸叔丁酯为引发剂,研究了苯乙烯自由基本体聚合的动力学过程,考察了引发剂浓度、温度、乙苯质量分数对聚合反应速率和聚苯乙烯分子量的影响.结果表明:在117℃下,聚合速率(Rp)对引发剂浓度的反应级数为0.42,对苯乙烯浓度的反应级数为1,聚合反应的表观活化能为54.8 kJ/mol.引发剂浓度、温度、乙苯质量分数的提高导致聚苯乙烯数均分子量分别下降了约30％、20％和15％,其中引发剂浓度的影响最为显著.     

凝胶型苯乙烯系离子交换树脂的强度及抗渗透性的影响因素研究 (I)

本文就单体组成中不同引发剂，链转移剂，环二烯，烯丙基类化合物和氧气等对凝胶型苯乙烯系阳离子交换树脂的强度和抗渗透性的影响进行了系统研究。结果显示，采用0．30％的过氧化2－乙基己酸叔丁酯（OT）和0．01％的过氧化苯甲酸特丁酯（CP）代替过氧化二苯甲酰（BPO作引发剂，或者加入0．02％的链转移剂十二烷基硫醇，均能够在一定程度上改善共聚物珠粒的结构均匀性，提高其合成的离子交换树脂的磨后圆球率和抗渗透性能。     

活性开环歧化合法合成带羧酸酯基功能高分子

由石油化工C5馏分提取得到的粗产品双环戊二烯(DCPD,83.9%)经精馏制成高纯度双环戊二烯(98.9%),解聚后制成环戊二烯(CPD).以CPD、丙烯酸叔丁酯(tBA)为原料经Diels-Alder反应合成得到了一种带叔丁氧羰基的降冰片烯衍生物-2-叔丁氧羰基-5-降冰片烯(BOCN).以钌卡宾络合物RuCl2(PCy3)2(=CHPh)为引发剂进行所合成降冰片烯基单体BOCN的活性开环歧化聚合(ROMP)反应,合成得到一种具有受控分子量及窄分子量分布的带羧酸酯基的反应性高分子.     

基于聚亚甲基的三嵌段聚合物:合成及其多孔薄膜的制备

利用叶立德活性聚合与原子转移自由基聚合(ATRP)相结合的方法制备得到基于聚亚甲基的两、三嵌段聚合物.首先由叶立德活性聚合及氧化反应得到末端羟基的聚亚甲基(PM-OH),再与2-溴异丁酰溴反应得到含溴末端的大分子引发剂(PM-Br),之后引发丙烯酸叔丁酯的ATRP聚合得到聚亚甲基-b-聚丙烯酸叔丁酯(PM-b-P-t-...     

含胺基功能性单体的聚合研究——Ⅻ.N-丙烯酰-N′-苯基哌嗪类的合成、光聚合及其作为氧化还原引发体系组分的研究

我们曾报道了含芳香叔胺基功能性单体的合成及其聚合的研究,这些单体都是既参与引发反应又参与聚合的“引发剂单体”。本文报道了一种含有芳香叔胺基的新单体——N-丙烯酰-N′-苯基哌嗪(APP)和N-甲基丙烯酰-N′-苯基哌嗪(MPP)的合成及其光聚合。由于APP或MPP含有芳香叔胺基,它们和过氧化苯甲酰(BPO)配合,     

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.     

三步法合成高封端率端氨基聚乳酸

叔丁氧羰基碳酸酐((Boc)2O)和氨基丙醇反应合成叔丁氧羰基氨基丙醇(Boc-氨基丙醇),以此为引发剂在辛酸亚锡的催化下,引发L-丙交酯开环聚合合成叔丁氧羰基氨基封端聚乳酸(BocNH-PLLA),叔丁氧羰基(Boc)经三氟乙酸处理脱除后得到端氨基聚乳酸(PLLA-NH2).以PLLA-NH2为大分子引发剂,引发ω-苄氧羰基L-赖氨酸-N-羧酸酐(ω-Z-L-Lysine-NCA)开环聚合,合成聚L-乳酸-聚ω-苄氧羰基L-赖氨酸两嵌段共聚物(P(LLA-LLz)).采用红外光谱(FT-IR)、核磁共振氢谱(1H-NMR)、凝胶渗透色谱(GPC)对聚合物结构进行了表征.结果表明:PLLA-NH2端基亲核性明显提高,可引发ω-Z-L-Lysine-NCA开环聚合制备嵌段共聚物,PLLA-NH2的合成方法简便,氨基封端率高,其分子量和单体与引发剂的摩尔比具有良好的线性关系.     

Surface functionalization of polystyrene to bind with FMRF peptides for novel biocompatibility

<正>A generic method was described to change surface biocompatibihty by introducing reactive functional groups onto surfaces of polymeric substrates and covalently binding them with biomolecules.A block copolymer with protected carboxylic acid functionality,poly(styrene-b-tert-butyl acrylate)(PS-PtBA),was spin coated from solutions in toluene on a bioinert polystyrene(PS) substrate to form a bilayer structure:a surface layer of the poly(tert-butyl acrylate)(PtBA) blocks that order at the air-polymer interface and a bottom layer of the PS blocks that entangle with the PS substrate.The thickness of the PtBA layer and the area density of tert-butyl ester groups of PtBA increased linearly with the concentration of the spin coating solution until a 2 nm saturated monolayer coverage of PtBA was achieved at the concentration of 0.4%W/W.The protected carboxylic acid groups were generated by exposing the tert-butyl ester groups of PtBA to trifluoroacetic acid (TFA) for bioconjugation with FMRF peptides via amide bonds.The yield of the bioconjugation reaction for the saturated surface was calculated to be 37.1%based on X-ray photoelectron spectroscopy(XPS) measurements.The success of each functionalization step was demonstrated and characterized by XPS and contact angle measurements.This polymer functionalization/modification concept can be virtually applied to any polymeric substrate by choosing appropriate functional block copolymers and biomolecules to attain novel biocompatibility.     

Environmentally responsive "hairy" nanoparticles: mixed homopolymer brushes on silica nanoparticles synthesized by living radical polymerization techniques

This article reports on the preparation of environmentally responsive "hairy" nanoparticles by growth of mixed poly(tert-butyl acrylate) (PtBA)/polystyrene (PS) brushes from silica particles using living radical polymerization techniques and subsequent hydrolysis of PtBA to produce amphiphilic mixed poly(acrylic acid) (PAA)/PS brushes. Silica particles were synthesized by the Stober process and were functionalized with an asymmetric difunctional initiator-terminated monolayer. Surface-initiated atom transfer radical polymerization of tBA was carried out in the presence of a free initiator. Kinetics study showed that the polymerization was well controlled. By cleaving PtBA off the particles, the molecular weights of the grafted and free polymers were found to be essentially identical. Mixed PtBA/PS brushes were obtained by the nitroxide-mediated radical polymerization of styrene from PtBA particles. The M(n) of the grafted PS was found to be the same as that of the free PS formed in the solution from the free initiator. Amphiphilic mixed PAA/PS brush-coated nanoparticles were synthesized from mixed PtBA/PS particles by hydrolysis of PtBA with iodotrimethylsilane. Tyndall scattering experiments and (1)H NMR study showed that the mixed PAA/PS particles can be dispersed and form a stable suspension in CHCl(3), a selective solvent for PS, and also in CH(3)OH, a selective solvent for PAA, demonstrating the capability of these hairy nanoparticles to undergo chain reorganization in response to environmental changes.     

带有可调通道的嵌段共聚物胶束对药物的控制释放

用聚丙烯酸叔丁酯-b-聚乙二醇(PtBA45-b-PEG114)和聚丙烯酸叔丁酯-b-聚4-乙烯基吡啶(PtBA60-b-P4VP80)制备了复合胶束. 该胶束在pH=2.5的酸性水溶液中形成以PtBA为核, PEG和P4VP为壳的稳定球型结构. 在pH=12时, 壳层的P4VP链段变为疏水, 塌缩在PtBA的核上形成内壳, PEG链段继续保持溶解状态, 与成核的PtBA连接并穿过塌陷的P4VP内壳, 形成胶束的冠, 由于PEG处于溶解状态, 其分子链间有比较大的空隙, 可以控制一些小分子通过, 在胶束的表面形成通道. 该通道类似于生物膜的蛋白通道, 可以控制PtBA核与外界进行能量或物质交换的速度. 以布洛芬为模型分子, 负载在胶束内进行药物控制释放研究的结果表明, 胶束表面的通道可以起到明显控制布洛芬释放速度的作用, 并且药物的释放速度与通道在胶束表面的比例成正比.     

Divergent synthesis of dendrimer‐like macromolecules through a combination of atom transfer radical polymerization and click reaction

This article describes a divergent strategy to prepare dendrimer‐like macromolecules from vinyl monomers through a combination of atom transfer radical polymerization (ATRP) and click reaction. Firstly, star‐shaped polystyrene (PS) with three arms was prepared through ATRP of styrene starting from a three‐arm initiator. Next, the terminal bromides of the star‐shaped PS were substituted with azido groups. Afterwards, the azido‐terminated star‐shaped PS was reacted with propargyl 2,2‐bis((2′‐bromo‐2′‐methylpropanoyloxy)methyl)propionate (PBMP) via click reaction. Star‐shaped PS with six terminal bromide groups was afforded and served as the initiator for the polymerization of styrene to afford the second‐generation dendrimer‐like PS. Iterative process of the aforementioned sequence of reactions could allow the preparation of the third‐generation dendrimer‐like PS. When the second‐generation dendrimer‐like PS with 12 bromide groups used as an initiator for the polymerization of tert‐butyl acrylate, the third‐generation dendrimer‐like block copolymer with a PS core and a poly (tert‐butyl acrylate) (PtBA) corona was afforded. Subsequently PtBA segments were selectively hydrolyzed with hydrochloric acid, resulting an amphiphilic branched copolymer with inner dendritic PS and outer linear poly(acrylic acid) (PAA). Following the same polymerization procedures, the dendrimer‐like PS and PS‐block‐PtBA copolymers of second generation originating from six‐arm initiator were also synthesized. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3330–3341, 2007     

Pattern formation in dewetting poly(tert-butyl acrylate)/polyhedral oligomeric silsesquioxane (POSS) bilayer films

The surface morphology of dewetting poly(tert-butyl acrylate) (PtBA) and trisilanolphenyl-POSS (TPP) bilayers has been studied as a function of time at 95 degrees C. For short annealing times, only the upper nanoparticle (TPP) layer dewets from the underlying PtBA layer. The number and lateral dimensions of the holes in the upper TPP layer increase with increasing annealing times, forming interconnected rim structures. At later annealing times, scattered holes that reach down into the PtBA layer are observed among the interconnected rim structures. Fractal nanofiller (TPP)-rich aggregates are found at the bottom of the scattered holes.     

Amphiphilic Seven-arm Star Triblock Copolymers with Diverse Morphologies in Aqueous Solution Induced by Crystallization and pH

Well-defined amphiphilic seven-arm star triblock copolymers containing hydrophobic crystalline poly(ε-caprolactone)(PCL) blocks, hydrophobic non-crystalline poly(tert-butyl acrylate)(PtBA) blocks and hydrophilic poly(ethylene glycol)(PEG) blocks were precisely synthesized by a combination of ring-opening polymerization(ROP), atom transfer radical polymerization(ATRP) and “click” reaction. Such star copolymers could self-assemble into “core-shell-corona” micelles and “multi-layer” vesicles depending on the fraction of each block. Meanwhile, the selective hydrolysis of middle PtBA blocks into the poly(acrylic acid)(PAA) blocks allowed the star block copolymers to further change their morphologies of aqueous aggregates in response to pH values.     

Block Copolymer Nanotubes

Rigid cylindrical micelles are made from polyisoprene-block-poly(2-cinnamoylethyl methacrylate)-block-poly(tert-butyl acrylate). The PI-PCEMA-PtBA polymer assembles to micelles with PI as the core, PCEMA as the shell, and PtBA as the corona. The cylindrical structure is fixed by photocrosslinking the PCEMA shell, and PCEMA-PtBA nanotubes are obtained by degrading the PI core with ozone (see scheme).     

Interfacial reactions in confinement: kinetics and temperature dependence of the surface hydrolysis of polystyrene-block-poly(tert-butyl acrylate) thin films

The effect of confinement on the kinetics of the surface hydrolysis of polystyrene-block-poly(tert-butyl acrylate) (PS(n)-b-PtBA(m)) thin films on oxidized silicon substrates in 3 M aqueous hydrochloric acid was systematically investigated. As shown by X-ray photoelectron spectroscopy (XPS) and contact angle measurements, a skin layer of acid-sensitive PtBA is present on the surface of PS(n)-b-PtBA(m) films, consistent with the lower surface tension of PtBA compared to that of PS. The thickness of the skin layer was determined by angle-dependent XPS as approximately 8 nm for PS(690)-b-PtBA(1210). Tapping mode atomic force microscopy showed an increasing surface coverage of swollen poly(acrylic acid)-rich globules with increasing hydrolysis time. Using ex situ Fourier transform infrared spectroscopy, the reaction kinetics was determined quantitatively as a function of temperature, polymer film thickness, thermal pretreatment of the films, and block copolymer composition. The initial stages of the hydrolysis can be described as a pseudo-first-order reaction under all conditions investigated. The corresponding rate constants were found to be 2 orders of magnitude lower than those reported for the hydrolysis of tert-butyl acetate in solution and depended linearly on the fraction of PtBA exposed at the surface. However, the polymer film thickness, thermal pretreatment of the films, block copolymer composition, and local composition did not affect the rate constants. The negative value of the activation entropy (DeltaS(298)++ = -103 J/mol K), determined according to the Arrhenius equation and transition state theory, indicates that the tightness of the transition state is more pronounced in the PS(n)-b-PtBA(m) film compared to reactions in solution. Thus, the spatial constraints due to the incorporation of the reactive ester groups in thin polymer films are responsible for the observed reduced reactivity.     

Synthesis of hyperbranched poly(tert‐butyl acrylate) by self‐condensing atom transfer radical polymerization of a macroinimer

Using 2‐hydroxyethyl α‐bromoisobutyrate as initiator, atom transfer radical polymerization (ATRP) of tert‐butyl acrylate leads to poly(tert‐butyl acrylate) (PtBA) with a hydroxyl group at one and a bromine atom at the other end. Esterification of the hydroxyl group of these heterotelechelic polymers with acryloyl chloride yields PtBA (M_n = 3 060) with a polymerizable double bond at one end and a bromine atom at the other end which can act as an initiator in ATRP (“macroinimer”). Self‐condensing ATRP of such a macroinimer leads to hyperbranched or highly branched PtBA. The polymer was characterized by GPC viscosity measurements. Even at M_w = 78 800, a rather low polydispersity index of M_w/M_n = 2.6 was obtained. A significantly lower value for the Mark‐Houwink exponent (α = 0.47 compared to α = 0.80 for linear PtBA) indicates the compact nature of the branched macromolecules.     

AMPHIPHILIC STAR-BLOCK COPOLYMERS BY IODIDE-MEDIATED RADICAL POLYMERIZATION

Amphiphilic star-block copolymers composed of polystyrene and poly(acrylic acid)were synthesized by iodide- mediated radical polymerization.Firstly,free radical polymerization of styrene was carried out with AIBN as initiator and 1,1,1-trimethyolpropane tri(2-iodoisobutyrate)as chain transfer agent,giving iodine atom ended star-shaped polystyrene with three arm chains,R(polystyrene)_3.Secondly,tert-butyl acrylate was polymerization using polystyrene obtained as macro-chain transfer agent,and star-block copolymer,R(polystyrene-b-poly(tert-butyl acrylate))_3 with controlled molecular weight was obtained.Finally,amphiphilic star-block copolymer,R(polystyrene-b-poly(acrylic acid))_3 was obtained by hydrolysis of R(polystyrene-b-poly(tert-butyl acrylate))_3 under acidic condition.