两亲性二嵌段共聚物MPEG44-b-Phe的合成及其在水溶液中的自组装

利用光气法,以三光气和苯丙氨酸为原料,合成了苯丙氨酸酸酐(b-Phe-NCA).用端氨基聚乙二醇单甲醚(MPEG-NH2)作大分子引发剂,引发b-Phe-NCA开环聚合,合成了不同分子量的聚乙二醇单甲醚-聚(L-苯丙氨酸)(MPEG44-b-Phe)AB型二嵌段共聚多肽.利用IR1、H-NMR、GPC对共聚物结构进行了表征.利用TEM研究了二嵌段共聚多肽MPEG44-b-Phe50及MPEG44-b-Phe7在水溶液中的自组装形态,结果表明合成出的两亲性二嵌段共聚物在水溶液中自组装形成胶束,随着嵌段共聚物中亲水嵌段含量的增高,共聚物溶水性增强,其在水溶液中的自组装形态更加均一.     

聚乙二醇甲醚-聚(D,L-乳酸)嵌段共聚物纳米胶束的制备

聚乙二醇甲醚-聚(D;L-乳酸)嵌段共聚物纳米胶束的制备;聚乙二醇单甲醚;两亲性二嵌段共聚物;纳米沉淀技术     

巯-炔加成可控修饰的两亲性嵌段共聚肽及其溶液自组装

以单甲氧基聚乙二醇伯胺(m PEG-NH2)作为大分子引发剂,引发γ-炔丙基-L-谷氨酸-N-羧基-环内酸酐(NCA)开环聚合的方法,合成了侧链上含有炔基的聚乙二醇-b-聚(γ-炔丙基-L-谷氨酸)两嵌段共聚物(PEG-b-PPLG).进一步通过巯基-炔基加成的"点击"化学方法,对两嵌段共聚物中聚氨基酸PPLG嵌段分别修饰了普通疏水性的饱和烷烃、具有超疏水性质的全氟代烷烃,并利用红外光谱、圆二色光谱、动态光散射和透射电子显微镜等技术,对合成的两嵌段共聚物在水溶液及有机溶剂四氢呋喃(THF)中的自组装性质进行了研究.研究发现两嵌段共聚物修饰前后,聚氨基酸嵌段在水和THF中都能保持一定的α-螺旋的构象,并进一步自组装形成以α-螺旋的聚氨基酸嵌段为内核、PEG嵌段为外壳的纳米聚集结构.     

用固体高分辨NMR研究聚(L-丙氨酸)-聚乙二醇单甲醚双嵌段共聚物的微相结构与链段运动

利用固体高分辨¹³CCP/MAS及二维WISE核磁共振技术研究了聚(L-丙氨酸)-聚乙二醇单甲醚双嵌段共聚物(MPEG-b-PLA)在固态下的微相结构和链段运动行为.结果表明,聚乙二醇链段在形成嵌段共聚物后结晶度明显下降,同时存在晶区和非晶区,从而表现出两种不同的运动状态.而聚乙二醇链段的引入对聚L-丙氨酸链段影响不大,嵌段共聚物中聚L-丙氨酸链段高度结晶,同时含有大量的α螺旋结构,分子链运动严重受限,估计聚L-丙氨酸链段的相区尺寸很小.     

聚己内酯/聚缩水甘油醚两亲性超枝状大分子的合成及表征

通过简单的两步反应, 合成出新型超枝状聚己内酯/聚缩水甘油醚嵌段共聚物. 以月桂醇为引发剂, 通过开环聚合反应合成羟基封端的聚己内酯; 将聚己内酯进一步和萘钾反应, 得到基于己内酯的大分子引发剂; 引发缩水甘油醚的聚合, 最终形成聚己内酯/聚缩水甘油醚嵌段共聚物. 通过核磁共振氢谱、红外光谱和葡聚糖凝胶色谱对聚合物进行定性表征. 结果表明, 所得到的聚合物既具有聚己内酯的特征峰, 又有聚缩水甘油醚的特征峰, 通过核磁共振氢谱计算出二者在嵌段共聚物中的比例. 在这些聚合物骨架上存在大量的羟基末端基团, 葡聚糖凝胶色谱表征得到单峰, 进一步证明聚合物为嵌段共聚物. 相对于单纯的聚己内酯, 这种聚合物结构的突出优势在于其具有大量可修饰的高活性端基基团, 通过对端基基团的后修饰, 可实现各类配体及多种药物的偶联, 使这种新型材料有可能应用于多功能靶向药物传递.     

化学酶法合成五嵌段聚合物及其自组装行为的研究

用酶促开环聚合与ATRP方法相结合,制备了聚甲基丙烯酸六氟丁酯-聚己内酯-聚乙二醇-聚己内酯-聚甲基丙烯酸六氟丁酯(PHFMA-b-PCL-b-PEG-b-PCL-b-PHFMA)五嵌段聚合物.首先用Novozym e 435作为催化剂合成了聚己内酯-聚乙二醇-聚己内酯三嵌段聚合物,然后通过端基官能化法合成了大分子引发剂,并用其引发甲基丙烯酸六氟丁酯(HFMA)的ATRP反应,合成了五嵌段聚合物.通过核磁和GPC证明了大分子引发剂和五嵌段共聚物的结构,五嵌段共聚物的GPC分析表明这种合成方法的可行.共聚物胶束的直径和大小通过动态光散射方法和原子力显微镜测试,五嵌段共聚物在水中的的自组装行为也被研究.结果证明胶束是球形,其平均直径为77 nm.聚合物在四氢呋喃中的浓度对聚合物的聚集形貌有很大的影响.     

聚L-丙氨酸-聚乙二醇嵌段共聚物纳米胶束的研究

分别以氨基聚乙二醇和氨基聚乙二醇单甲醚为大分子引发剂,采用开环聚合的方法合成了两亲性聚L-丙氨酸-聚乙二醇(PAE)和聚L-丙氨酸-聚乙二醇单甲醚(PAME)两种嵌段共聚物,其结构经1H NMR,IR,DSC,GPC等表征;利用园二色技术研究了其在水溶液中的二级结构,用芘荧光探针技术研究了其胶束的形成及其临界胶束浓度(CMC),利用透射电镜研究了胶束的形态。结果表明,在水溶液中共聚物链以α-螺旋构象形式存在,在一定条件下嵌段共聚物PAE-1,PAE-2,PAME-1和PAME-2能够形成球形的稳定胶束,PAE-1形成胶束的CMC为3.36×10-5mol.L-1,CMC值受嵌段类型和共聚物中聚L-丙氨酸链段含量的影响。     

聚谷氨酸苄酯-聚乙二醇-聚谷氨酸苄酯嵌段共聚物的圆二色光谱分析

用三乙胺和双端氨基聚乙二醇分别引发经酯化、环化等处理的谷氨酸开环聚合制备聚谷氨酸苄酯（PBLG）和聚谷氨酸苄酯-聚乙二醇-聚谷氨酸苄酯嵌段共聚物（PBLG-PEG-PBLG,GEG）。采用圆二色光谱对聚合物溶液的旋光性进行分析,以确定共聚物中PBLG嵌段的构型和含量。结果表明,均聚物和共聚物中的PBLG嵌段都以α-螺旋构型存在,中间的PEG不扰乱其构型,通过聚合物的圆二色性（circular dichroism,CD）计算出的PBLG嵌段含量与核磁共振（nuclear magnetic resonance,NMR）所得结果基本一致。     

聚L-丙氨酸-聚乙二醇嵌段共聚物的胶束化行为研究

以氨基聚乙二醇单甲醚(MPEG-NH₂)为大分子引发剂, 采用开环聚合方法合成了聚L-丙氨酸-聚乙二醇嵌段共聚物(PAME), 并对其结构进行了表征; 用圆二色谱(CD)研究了嵌段共聚物在水溶液中的二级结构, 用芘荧光探针技术研究了共聚物胶束的形成及其临界胶束浓度(CMC), 利用动态光散射(DLS)和透射电镜(TEM)研究了胶束的粒径分布和形态. 结果表明, 在水溶液中共聚物链以α-螺旋构象形式存在, 在一定条件下嵌段共聚物能够形成球形的稳定胶束, PAME-1形成胶束的CMC为1.99×10^-5 mol/L, CMC值受共聚物中聚L-丙氨酸(PLA)链段含量的影响.     

茂金属化合物/Zn/BDGE/MAO催化体系合成aPS-b-P(S-co-E)-b-PE嵌段共聚物的研究

采用单茂钛化合物CpTiCl3,有机环氧化合物1,4-丁二醇二缩水甘油基醚(BDGE),金属锌(Zn)及甲基铝氧烷(MAO)为催化体系,通过自由基聚合和配位聚合机理合成无规聚苯乙烯-b-聚(苯乙烯-co-乙烯)-b-聚乙烯(aPS-b-P(S-co-E)-b-PE).探讨了温度、时间、乙烯压力及Al/Ti摩尔比对共聚合的影响.所得嵌段共聚物采用DSC,WAXD,GPC和13C-NMR等手段进行了表征.结果表明该共聚物是苯乙烯/乙烯嵌段共聚物,聚苯乙烯链段是无规的,聚乙烯链段具有结晶性.     

SYNTHESIS AND CHARACTERIZATION OF NOVEL CHIRAL SMECTIC C(Sc*) PHASE SHISH-KEBAB TYPE LIQUID CRYSTALLINE BLOCK COPOLYMERS*

A new series of chiral shish-kebab type liquid crystal block copolymers that form the smecticC(Sc~*) phase was synthesized by solution polycondensation. The copolymers were characterized by GPC.DSC. TG, POM. X-ray diffraction and polarimeter. The copolymers 7 entered into liquid crystal phase whenthey were heated to their melting temperatures (T_m) and the copolymers 8 were in liquid crystal phase at roomtemperature with low viscosities. The smectic sanded texture or focal-conic texture were observed on POM.All the chiral block copolymers showed high optical activity. No racemization has happened. Temperature-variable X-ray diffraction study together with POM and polarimetric analysis realized that they are chiralsmectic C(Sc~*) phase. Thus we offer in this report the first example of shish-kebab type liquid crystal blockcopolymers that form a chiral smectic C(Sc~*) phase. The variation of melting and isotropization temperatureswith molecular structure was also discussed.     

Induction of a chiral nematic phase in smectic polymers

A number of new photosensitive copolyacrylates of different composition were obtained by the copolymerization of chiral photochromic benzilidene-p-menthane- 3-one acrylic monomers with a smectogenic monomer containing a hexyloxyphenylbenzoate mesogenic group. The chiral, photochromic monomers differ by the length of the aliphatic spacer and the aromatic fragment. It was found that the introduction of a small number of chiral units into the copolymers (5 mol%) leads to the “degeneration” of the smectic C phase, which characterizes the hexyloxyphenylbenzoate homopolymer, and to the formation of the smectic A phase. An unusual effect of chiral nematic phase induction was observed for copolymers containing chiral side groups with two ring aromatic fragments. It should be pointed out that the chiral nematic phase does not occur in the case of the homopolymers of both initial comonomers. An explanation of this effect, based on the consideration of the chemical structure of the chiral and hexyloxyphenylbenzoate units, was suggested. The optical properties of cholesteric copolymers were investigated; the helical twisting power of the chiral groups of different structures was calculated. The possibility of using such copolymers as new photosensitive materials was demonstrated. Received: 16 December 1999/Accepted: 1 February 2000     

侧基对N-炔丙基酰胺螺旋共聚物光学活性的影响

设计并合成了5个系列的带有不同侧基的手性-非手性N-炔丙基酰胺共聚物,以铑有机配合物为催化剂对单体实施聚合反应得到高产率(>95%)的共聚物,聚合物具有高立构规整性(cis-含量高于94%).利用圆二色(CD)及紫外-可见吸收(UV-Vis)光谱技术对共聚物的二级结构及光学活性进行了表征,当非手性单体的酰胺侧基体积适中时,共聚物具有较高的光学活性,部分共聚物的光学活性甚至高于纯手性聚合物.表明通过选择合适的手性-非手性共聚单体及单体配比,可获得具有高光学活性的螺旋聚合物.     

A comparative study of photo-optical behaviour of photosensitive chiral copolymers with cholesteric mesophases induced in nematogenic and smectogenic matrices

The photo-optical behaviour of two series of chiral photochromic acrylic copolymers with a chiral nematic phase has been studied. These copolymers contain identical chiral photochromic units, but have different structures of the phenyl benzoate mesogenic side groups which are responsible for the development of LC phases. This approach allowed us to examine specific features of the photo-optical behaviour of the copolymers as a function of the nature of the LC 'matrix' in which the cholesteric phase was induced. The action of UV irradiation was shown to lead to the E-Z isomerization of the chiral side groups and, as a consequence, to untwisting of the cholesteric helix of the copolymers. For copolymers of both series, the effective quantum yields of this photochemical process were calculated. In the case of copolymers in which the cholesteric mesophase is induced in a smectogenic matrix, the corresponding values of the quantum yield are lower and depend slightly on temperature. A plausible explanation of the above phenomena is suggested.     

A comparative study of photo-optical behaviour of photosensitive chiral copolymers with cholesteric mesophases induced in nematogenic and smectogenic matrices

The photo-optical behaviour of two series of chiral photochromic acrylic copolymers with a chiral nematic phase has been studied. These copolymers contain identical chiral photochromic units, but have different structures of the phenyl benzoate mesogenic side groups which are responsible for the development of LC phases. This approach allowed us to examine specific features of the photo-optical behaviour of the copolymers as a function of the nature of the LC 'matrix' in which the cholesteric phase was induced. The action of UV irradiation was shown to lead to the E-Z isomerization of the chiral side groups and, as a consequence, to untwisting of the cholesteric helix of the copolymers. For copolymers of both series, the effective quantum yields of this photochemical process were calculated. In the case of copolymers in which the cholesteric mesophase is induced in a smectogenic matrix, the corresponding values of the quantum yield are lower and depend slightly on temperature. A plausible explanation of the above phenomena is suggested.     

Templating mesoporous silica with chiral block copolymers and its application for enantioselective separation

In this paper we describe the synthesis of chiral mesoporous silica based on chiral block copolymers of poly(ethylene oxide) and of d-phenylalanine (PEO-b-D-Phe) as a surfactant template. The resulting porous structures are characterized by nitrogen sorption experiments, transmission electron microscopy, and small-angle XRD. It is shown that chiral block copolymers of PEO-b-D-Phe are effective as a surfactant template for the preparation of silica materials with highly ordered periodic mesoporous structures of hexagonal symmetry with a pore size of ca. 5 nm and high surface areas of ca. 700 m2/g. The enantioselectivity feature of this porous silica, after the extraction of the chiral copolymers, was examined by selective adsorption of enantiomers and racemic solutions of valine. The selective adsorption was measured by circular dichroism (CD) spectroscopy. A chiral selectivity factor of 2.34 was found with the D enantiomer of valine adsorbed preferably.     

新型光活性串型液晶共聚物合成与表征

以对苯二甲酰氯,２ ,５ 二［４ （（Ｓ） ２ 甲基丁氧基） 苯甲酰氧基］ 对苯二酚和己二醇为单体,采用溶液共缩聚的方法,合成了一系列新的光活性串型液晶共聚物．共聚物通过ＧＰＣ、ＤＳＣ、ＴＧ、ＷＡＸＤ、偏光显微镜和旋光仪等方法表征．发现所有的共聚物加热至各自的熔点以上都能形成液晶态,在液晶态可以观察到沙地织构或破碎焦锥织构．通过变温Ｘ 射线衍射证明它们为手性近晶Ｃ（Ｓ＊Ｃ） 相．所有共聚物的熔点（ Ｔｍ） 和液晶态清亮点（ Ｔｉ） 随共聚物中己二醇用量的改变呈规律性变化．共聚物有很高的旋光性,在合成反应中旋光性保持．     

New types of multifunctional liquid crystalline photochromic copolymers for optical data recording and storage

A new family of multifunctional chiral‐photochromic liquid crystalline (LC) copolymers containing mesogenic, chiral and photoactive groups were synthesized. The new principles of photo‐regulation of the helical supramolecular structure and optical properties of the binary and ternary chiral‐photochromic LC polymers based on the change of helical twisting power of the chiral‐photochromic monomer units, the dual photochromism and photochemical spectral gap burning were developed. It was shown, that the introduction of small amount of low‐molar‐mass chiral‐photochromic dopants in chiral LC copolymers having different helix signs followed by light irradiation permits one to twist or untwist the helical supramolecular structure. The synthesized polymers are shown to be promising candidates for colour data recording and storage.     

Three-dimensionally packed nanohelical phase in chiral block copolymers

Chirality-driven microphase-separated morphology, poly(l-lactide) (PLLA) left-handed nanohelices hexagonally packed in PS matrix, was obtained from chiral diblock copolymers, poly(styrene)-b-poly(l-lactide). This is perhaps for the first time; the helical superstructures of chiral block copolymers were generated in the bulk and self-assembled to a two-dimensionally (2D) packed lattice. Now, the analyses of block copolymer thermodynamics should be complicated by the chiral entities of constituted components. Orderly packed nanohelical channels can be obtained after hydrolysis, and this provides new opportunities for block copolymer applications in the fields of nanosciences.     

Asymmetric radical copolymerization of S(−)-α-phenethylammonium butadiene 1-carboxylate with styrene

Radical copolymerization of S(?)-α-phenethylammonium butadiene 1-carboxylate (S-PBu) with styrene was performed in methanol, using azo-bis-isobutyronitrile as initiator. It was confirmed that the copolymers had trans 1,4 units of S-PBu; the copolymers after removal of chiral side chain were optically active. From CD spectra of the copolymers after removal of chiral amine from the side chain, it was found that the asymmetric induction occurred in the copolymer main chain. The copolymerization parameters of S-PBu were determined and are discussed.