原子力显微镜与透射电镜对比研究嵌段共聚物微相分离形态

嵌段共聚物微观相分离形态结构由于其理论与应用中的重要性一直是人们研究的热点 [1] .本文研究的聚苯乙烯 -聚乙烯 /聚丁烯 -聚苯乙烯三嵌段共聚物 (SEBS)为聚苯乙烯 -聚丁二烯 -聚苯乙烯 (SBS)饱和加氢后的产物 .由于中间嵌段中的双键大多已加氢饱和 ,过去一直没有合适的染色剂进行染色 ,所以在 2 0世纪 80年代中期以前 ,SEBS形态结构未见文献报道 [1] .近年来 ,由于新型染色剂 Ru O4 的应用 ,使得用透射电镜 (TEM)观察其微相分离形态成为可能 .　　随着对嵌段共聚物形态结构认识程度深入 ,人们迫切希望能有新的手段提供更加丰富的…     

采用反应挤出三次加料法合成苯乙烯/异戊二烯/苯乙烯

以同向啮合双螺杆挤出机为反应器,采用苯乙烯和异戊二烯为聚合单体,以正丁基锂为引发剂,采用三次加料法合成苯乙烯/异戊二烯/苯乙烯(SIS)三嵌段热塑性弹性体.氢核磁共振(1H NMR)谱分析结果表明,共聚物中聚异戊二烯嵌段以1,4-结构为主.采用四氧化锇催化双氧水氧化降解聚合物分子链,利用凝胶渗透色谱对氧化降解后的聚苯乙烯碎片进行分析,证明共聚物分子为(聚苯乙烯-聚异戊二烯-聚苯乙烯)(PS-PI-PS)三嵌段结构.动态力学分析(DMA)及透射电子显微镜(TEM)分析结果表明,SIS具有两相分离结构.拉伸试验结果表明,共聚物拉伸强度与苯乙烯含量有关.     

丙烯腈-苯乙烯嵌段共聚物的RAFT聚合与表征

以S,S'-二(α,α '-二甲基-α″-乙酸)三硫代碳酸酯(TRIT)为链转移剂,利用可逆加成断裂链转移自由基聚合(RAFT)制备了窄分布的端羧基大分子链转移剂——聚苯乙烯和聚丙烯腈.以大分子链转移剂为RAFT试剂,引发苯乙烯或丙烯腈单体的RAFT聚合,进一步得到聚丙烯腈-聚苯乙烯-聚丙烯腈(PAN-b-PS-b-PAN)和聚苯乙烯-聚丙烯腈-聚苯乙烯(PS-b-PAN-b-PS)三嵌段共聚物.通过1 H-NMR、FT-IR、凝胶渗透色谱(GPC)对所得产物的结构和分子量进行了袁征,通过原子力显微镜(AFM)和拉曼光谱(Raman)研究了嵌段共聚物薄膜的微相分离结构与热解行为.结果表明:所得产物中除PAN-b-PS-b-PAN外,分子量分布均小于1.2.嵌段共聚物薄膜经250℃热稳定化与600℃热解处理后,碳化并形成了规整的石墨结构,微区尺寸在75 nm左右.     

温敏聚苯乙烯接枝聚异丙基丙稀酰胺梳型共聚物的合成

采用氯化亚铜为催化剂, 1,1,4,7,10,10-六甲基三亚乙基四胺(HMTETA)为配体, 溴代聚苯乙烯为大分子引发剂,以异丙基丙稀酰胺为单体进行原子转移自由基聚合(ATRP), 合成窄分布的聚苯乙烯接枝聚异丙基丙稀酰胺聚合物. 红外光谱(IR)和氢核磁共振波谱(1H NMR)证明了接枝聚合物的结构. 凝胶渗透液相色谱(GPC)(用聚苯乙烯作为标样)研究发现, 接枝共聚物的分子量分布是单分散的, 数均分子量为19815 g/mol. 差示扫描量热法(DSC)研究表明, 由于疏水的异丙基和胺基的氢键作用, 接枝共聚物的玻璃化转变温度比作为原料的聚苯乙烯提高了16.0℃. 报道了温敏的以溴代聚苯乙烯为骨架的接枝共聚物的成功制备.     

聚苯乙烯-乙丙共聚物两嵌段共聚物的组成分析

本文用红外光谱(IR)的工作曲线法及傅里叶变换红外光谱(FT-IR)差谱法,分析了多单体嵌段共聚物聚苯乙烯-乙丙共聚物PS-b-EPR的组成,包括聚苯乙烯段的含量和乙丙共聚物段的乙丙组成。     

聚氧化乙烯-聚苯乙烯-聚氧化乙烯三嵌段共聚物的微相分离与结晶

本工作研究了多分散和单分散聚氧化乙烯-聚苯乙烯-聚氧化乙烯三嵌段共聚物(PEO-PS-PEO)的结晶行为,及这些试样按非晶型嵌段共聚物进行微相分离后再结晶的结晶特点.     

降冰片烯端基聚苯乙烯大分子单体的合成

近年来,大分子单体的合成及其共(自)聚合正日渐成为高分子合成中非常活跃的领域。本试验室曾合成了具有烯丙基端基的聚苯乙烯大分子单体(PS-allyl),并将其与乙烯、丙烯共聚合得到了乙丙共聚物(EPR)为主干、聚苯乙烯(PS)为支链的接校共聚物EPR-g-PS。本工作以5-溴甲基-2-降冰片烯(BrMNB)与聚苯乙烯阴离子(PS^-)偶合,制备具有降冰片烯端基的聚苯乙烯大分子单体(PS-NB)。     

聚苯乙烯微球表面接枝丙烯腈的研究

采用分散聚合法制备出平均粒径为3.85 μm的窄分布聚苯乙烯微球， 并在此基础上引入第二单体丙烯腈进行共聚反应， 制备出平均粒径为4.02 μm的窄分布苯乙烯-丙烯腈共聚物微球. 对聚苯乙烯微球和苯乙烯-丙烯腈共聚物微球进行了形貌及粒径、红外光谱、差示扫描量热法(DSC)分析， 结果表明丙烯腈基团均匀分布在聚苯乙烯微球表面， 提高了聚苯乙烯微球表面的极性.     

嵌段共聚物薄膜中条纹形态的螺旋结构

利用溶液滴膜的方法在云母表面制备聚苯乙烯-聚异戊二烯-聚苯乙烯(SIS)三嵌段共聚物薄膜, 用原子力显微镜(AFM)观察其表面形态. 发现共聚物经微相分离, 在薄膜中形成平行于表面的条纹形态, 相周期约(38±5) nm, 并且观察到条纹环绕形成的螺旋图案, 图案尺寸超过1 μm. 在螺旋中心某一组分形成闭合端, 而其它区域条状相沿螺旋切线方向平行排列. 嵌段共聚物溶液成膜过程中, 螺旋图案的产生是由于微相分离过程耦合流体力学相互作用产生的不稳定性所导致.     

两亲性嵌段共聚物的自组装及载药胶束的研究

采用可逆-加成-断裂链转移自由基聚合(RAFT)技术合成了两亲性嵌段共聚物聚苯乙烯-b-聚甲基丙烯酸聚乙二醇单甲醚-b-聚苯乙烯(PSt-b-POEOMA-b-PSt),通过FT-IR、1 HNMR、GPC确定共聚物的结构。将三个具有不同嵌段比的共聚物在水溶液中自组装,通过透射电子显微镜(TEM)观察得到的胶束的形貌,发现随着亲水性嵌段的比例减小,胶束的直径略微减小。通过透析方法,以共聚物作为载体,负载维生素E,TEM观察载药胶束的形貌,仍然为核-壳状的球形胶束。差示扫描量热仪(DSC)测试共聚物载药胶束前后的热性能,发现药物分子在载入内核的过程中,聚苯乙烯的玻璃化转变温度(Tg)有所降低。通过紫外(UV)分析计算得出共聚物的药物负载量(DLC)为70%～80%。     

SEBS的氯甲基化及羟甲基化＊

Hydroxymethyl groups were introduced into hydrogenated poly(styrene-block-butadiene-block-styrene)(SEBS) via chemical modification of the PS blocks by a simple three-step procedure,i.e.,chloromethylation via Friedel-Crafts reaction with stannic chloride(SnCl₄) as catalyst in chloroform solution in the presence of trioxane and chlorotrimethylsilane,followed by esterification and hydrolysis by using phase transfer catalyst TBAB.¹H NMR,FTIR,SEC and elemental analysis were employed to characterize the products.The results show that the degree of functionalization could be controlled in the first step,and the convertions of chloromethyl to ester and ester to hydroxyl were complete.Meanwhile molecular weight distribution of the product was still narrow.Crosslinking could be avoided when the polymer concentration was kept lower than its overlap concentration.     

用SN型催化剂合成苯乙烯一丙烯嵌段共聚物的研究──Ⅰ．聚合条件对共聚合反应的影响

用稀土化合物改性的钛系载体催化剂（ＳＮ催化剂）进行苯乙烯和丙烯顺序嵌段共聚合（Ｓｅｑｕｅｎｔｉａｌｂｌｏｃｋｃｏｐｏｌｙｍｅｒｉｚａｔｉｏｎ）的研究．考察了苯乙烯预聚时间、单体比、外加给电子体（ＥＢ）、烷基铝浓度、催化剂浓度和聚合温度等条件对共聚合的影响．发现外加酯（ＥＢ）降低了共聚合反应催化活性，在ＥＢ／Ｔｉ摩尔比为５范围内，外酯有助于提高嵌段共聚物（ｉＰＳ—ｂ—ｉＰＰ）中ＰＳ段和ＰＰ段的等规度及增加苯乙烯链节含量．ＳＮ型催化剂对苯乙烯一丙烯嵌段共聚合有较高的催化活性，催化效率在１００ｇ聚合物／ｇ－Ｔｉ以上．共聚物通过溶剂革取分级除去均聚物后，所得嵌段共聚物中苯乙烯链节含量可在１５～８５ｍｏｌ％之间调节．其结构表征续见第ＩＩ报．     

Dynamic kinetic resolution of secondary alcohols combining enzyme-catalyzed transesterification and zeolite-catalyzed racemization

Hydrophobic zeolite beta containing low concentrations of Zr or Al was found to be a good catalyst for the racemization of 1-phenylethanol. The formation of styrene as a side product could be minimized by reducing the metal concentration in the zeolite beta. Combined with an immobilized lipase from Candida antarctica, the dynamic kinetic resolution of 1-phenylethanol to the (R)-phenylethylester can be achieved with high yield and selectivity. The reaction was best conducted in toluene as solvent at 60 degrees C, with higher temperatures leading to a loss in the enantioselectivity of the formed ester. By using high-molecular-weight acyl-transfer reagents, such as vinyl butyrate or vinyl octanoate, a high enantiomeric excess of the product esters of 92 and 98 %, respectively, could be achieved. This is attributed to a steric effect: the bulky ester is less able to enter the pore space of the zeolite catalyst where the active sites for racemization are localized. Close to 100 % conversion of the alcohol was achieved within 2 h. If the more common acyl donor, isopropenyl acetate, was used, the enantiomeric excess (ee) of the formed ester was only 67 %, and the reaction was considerably slower.     

Preparation of reactive block copolymers and their transformation to hollowed nanostructures

A novel polymeric hollow nanostructure was generated using micellar template method through a three‐step procedure. First, the block copolymers were synthesized via ring‐opening metathesis polymerization by sequentially adding monomers 7‐oxanorborn‐5‐ene‐exo‐exo‐2,3‐dicarboxylic acid dimethyl ester and the mixture of norbornene and 2,3‐bis(2‐bromoisobutyryloxymethyl)‐5‐norbornene in chloroform, and also atom transfer radical polymerization of 4‐(3‐butenyl)styrene was carried out by using the as‐obtained block copolymer poly(7‐oxanorborn‐5‐ene‐exo,exo‐2,3‐dicarboxylic acid dimethylester)‐block‐poly(norbornene‐co‐2,3‐bis(2‐bromoisobutyryloxymethyl)‐5‐norbornene as macroinitiator to afford a graft copolymer bearing poly(4‐(3‐butenyl)styrene) branch poly(7‐oxanorborn‐5‐ene‐exo,exo‐2,3‐dicarboxylic acid dimethylester)‐block‐poly(norbornene‐co‐2,3‐bis(2‐bromoisobutyryloxymethyl)‐5‐norbornene)‐graft‐poly(4‐(3‐butenyl)styrene). Second, the shell‐crosslinked micelles were prepared by ruthenium‐mediated ring‐closing metathesis of poly(4‐(3‐butenyl)styrene) branches in intramicelle formed from the copolymers self‐assembly spontaneously in toluene. Finally, the hollowed spherical nanoparticles were presented by removing the micellar copolymer backbone through the cleavage of the ester bonds away from the crosslinked network of branches. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Catenated PS–PMMA Block Copolymers via Supramolecularly Templated ATRP Initiator Approach

A novel route to synthesize catenated macrocyclic PS–PMMA block copolymers is demonstrated via combination of supramolecular chemistry and controlled radical polymerization (CRP). Polymerization of styrene with bromopropionate ester initiator coupled with phenanthroline Cu(I) complex affords a four arm PS macroinitiator, which upon further chain extension by polymerization of MMA generates a four arm PS–PMMA block copolymer. Intramolecular coupling of PS–PMMA–Br arms via low temperature styrene‐assisted atom transfer radical coupling (ATRC) leads to the formation of PS–PMMA catenand, which generates the metal‐free catenated macrocyclic PS–PMMA block copolymer after removal of Cu metal. The interlocked structures of catenated block copolymers are confirmed by GPC, NMR, and AFM image analysis.     

Synthesis of Syndiotactic Polystyrene/Atactic Polypropene Block Copolymer in the presnece of Half-sandwich Titanocene Catalysts

Some highly active η5-pentamethylcyclopentadienyltribenzyloxy titanium complexes [Cp*Ti(Obz)3] activated by modified methylaluminoxane (mMAO) were prepared and used as the catalyst for styrene syndiospecific polymerization and propene atactic polymerization. Styrene could be copolymerized with propene when the propene was prepolymerized for a period, to which styrene and tri-isobutylaluminum (TIBA) were then added. The titled block copolymer together with the related homopolymers was obtained. The copolymerization porducts can be divided into the homopolymers and the copolymer by successive solvent extraction with boiling butanone, heptane and tetrahydrofuran (THF), and each fraction was characterized by 13C NMR, DSC and WAXD. It was found that aPS and aPP were soluble in boiling butanone and heptane respectively. The block copolymer (sPS-b-aPP) composed of syndiotactic polystyrene segment was soluble in boiling THF and the residue was chiefly sPS.     

壳聚糖席夫碱钯配合物催化碘代苯与苯乙烯交叉偶联反应的研究

水杨醛与壳聚糖反应制得壳聚糖席夫碱配体,此配体与钯盐反应得到壳聚糖席夫碱钯催化剂.研究了该催化剂对碘代苯(PhI)与苯乙烯偶联生成反式-二苯乙烯的催化性能.考察了不同反应因素(原料比、缚酸剂种类及其用量、反应温度、溶剂、催化剂用量、反应时间)对该反应的影响,由此确定了该催化反应的最佳反应条件.该催化剂经过滤分离、溶剂洗涤,循环使用6次仍有较高的催化活性,该催化剂对取代碘苯与苯乙烯的反应也有较高的催化活性.     

Synthesis and Characterization of ABBA Block Copolymer of Glycolide and ε-Caprolactone

A biodegradable ABBA block copolymer was synthesized via the ring-opening co-polymerization of ε-caprolactone(CL, B) and glycolide(A) by means of step polymerization in the presence of ethylene glycol as an initiator and stannous octanoate as a catalyst at 110 ℃ for 48 h. The molecular length of the PCL pre-polymer(BB) could be adjusted by controlling the molar ratio of the ethylene glycol initiator to ε-caprolactone monomer. The structure and the composition of the block copolymer were determined by the weight ratio of the monomer glycolide(A) to PCL pre-polymer(BB). The block copolymers were characterized by 1H NMR, GPC, DSC and X-ray. The results confirm the successful synthesis of an ABBA block copolymer.     

Synthesis of AB‐type block copolymers containing benzoxazole and anthracene groups by ATRP and fluorescent property

Two functional monomers, methacrylic acid 4‐(2‐benzoxazol)‐benzyl ester (MABE) containing the benzoxazole group and 4‐(2‐(9‐anthryl))‐vinyl‐styrene (AVS) containing the anthracene group were synthesized by rational design. The MABE was polymerized via atom transfer radical polymerization (ATRP) using ethyl 2‐bromoisobutyrate (EBIB) as initiator in CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) catalyst system; block copolymers poly(MABE‐b‐AVS) was obtained, which was conducted by using poly(MABE) as macro‐initiator, AVS as the second monomer, and CuBr/PMDETA as catalyst. The constitute of two monomers in block copolymers poly(MABE‐b‐AVS) by ATRP could be adjusted, that is the constitute of the benzoxazole group and the anthracene group could be controlled in AB‐type block copolymers. Moreover, the fluorescent properties of homopolymers poly(MABE) and block copolymers poly(MABE‐b‐AVS) were discussed herein. With the excitation at λ_ex = 330 nm, the fluorescent emission spectrum of poly(MABE) solution showed emission at 375 nm corresponding to the benzoxazole‐based part; with the same excitation, the fluorescent emission spectrum of poly(MABE‐b‐AVS) solution showed a broad peek at 330–600 nm when the monomer AVS to the total monomers mole ratio was 0.31, and the fluorescent emission spectrum of poly(MABE‐b‐AVS) in film state only showed one peak at 525 nm corresponding to the anthracene‐based unit that indicated a complete energy transfer from the benzoxazole group to the anthracene group. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3894–3901, 2007