Triblock and Radial Star-Block Copolymers Comprised of Poly(ethoxyethyl glycidyl ether), Polyglycidol,Poly(propylene oxide) and Polystyrene Obtained by Anionic Polymerization Initiated by Cs Initiators

The anionic polymerization of ethoxyethyl glycidyl ether (EEGE) initiated by cesium alkoxide was studied. The ring-opening polymerization of EEGE in the presence of cesium alkoxide of 1-methoxy-2-ethanol does not involve any side reactions. The presence of an additional alcohol leads to a significant increase of the initiator efficiency. Aqueous solutions of poly (ethoxyethyl glycidyl ether) (PEEGE) exhibit lower critical solution temperature (LCST), and the polymer solubility in water is extremely sensitive to its MW. Two novel types of block copolymers based on PEEGE were synthesized: triblock-copolymers of ABA (A′:BA′) structure, where A is the PEEGE block, A′ polyglycidol (PG) and B the polypropylene oxide (PPO) block, and A₂S (A′₂S) and A₄S (A′₄S) heteroarm stars, where S is the polystyrene block. The synthesis of the ABA block was performed by polymerization of EEGE initiated by bi-functional PPO/Cesium alkoxide macroinitiator. The PEEGE blocks were converted into PG blocks by successful cleavage of the ethoxyethyl group. Polystyrene/PEEGE and polystyrene/PG three- and five- heteroarm star copolymers were synthesized by a coupling reaction between well-defined chain-end-functionalized polystyrenes carying dendritic benzyl bromide moieties with living anionic polymers of PEEGE with one cesium alkoxide terminal group. The coupling reaction proceeds quantitatively without any side reactions, and thus series of star-branched polymers can be systematically synthesized. Polystyrenes with two or four PG arms have been obtained after the cleavage of the protecting group. The compact structure of these multi-arm star polymers and their amphiphilic character leads to the formation of nanoparticles in aqueous solution with rather uniform size distribution and a mean diameter of 15 nm.     

两亲性树状聚合物*

树状聚合物及其功能化是近年来高分子科学界的研究热点之一。本文综述了不同类型的树状聚合物,分别有聚酯、聚丙三醇、聚乙烯亚胺等超支化聚合物,聚酰胺-胺、聚丙烯亚胺等树枝状聚合物。通过对树状聚合物末端大量官能团的亲水（亲油）改性可以制备两亲性树状聚合物,改性方法主要有酰胺化反应、酯化反应、麦克尔加成反应等。与通过缩聚反应所得到的上述树状聚合物不同,近年来配位聚合领域出现的通过“链行走”机理形成的树状聚乙烯,引起了高度关注,这方面着重介绍了乙烯与极性单体直接共聚合或者采用链行走与原子转移自由基聚合联用制备两亲性树状乙烯聚合物。最后对两亲性树状聚合物领域的发展前景进行了展望。     

Thermoresponsive Polyphosphoester via Polycondensation Reactions: Synthesis,Characterization, and Self-Assembly

Using a novel strategy, amphiphilic polyphosphoesters based on poly(oxyethylene H-phosphonate)s (POEHP) with different poly(ethylene glycol) segment lengths and aliphatic alcohols with various alkyl chain lengths were synthesized using polycondensation reactions. They were characterized by ¹H NMR, ¹³C {H} NMR ³¹P NMR, IR, and size exclusion chromatography (SEC). The effects of the polymer structure on micelle formation and stability, micelle size, and critical micelle temperature were studied via dynamic light scattering (DLS). The hydrophilic/hydrophobic balance of these polymers can be controlled by changing the chain lengths of hydrophilic PEG and hydrophobic alcohols. A solubilizing test, using Sudan III, revealed that hydrophobic substances can be incorporated inside the hydrophobic core of polymer associates. Loading capacity depends on the length of alkyl side chains. The results obtained indicate that these structurally flexible polymers have the potential as drug carriers.     

盐对刷型两亲聚合物聚集行为的调控作用

两亲聚合物奇异的功能特性源于分子独特的骨架结构和在溶液中的自组装聚集行为. 本文向以2-丙烯酰胺基-十二烷基磺酸(AMC₁₂S)与2-丙烯酰胺基-2-甲基丙磺酸(AMPS)进行无规共聚所制备的AMPS-AMC₁₂S刷型两亲聚合物溶液体系中引入不同用量的NaCl, 采用稳态荧光、动态光散射(DLS)和透射电子显微镜(TEM)系统考察NaCl 对聚合物聚集行为的调控作用. 研究发现, 聚合物结构中疏水侧链含量越低, NaCl 对聚集行为的调控作用越强; NaCl浓度增加会明显降低聚合物的临界聚集浓度; 与此同时, 聚合物分子链自组装由分子间的聚集方式向分子内的聚集方式转变, 形成的聚集形态由大型多分子聚集体变化为尺寸数百分之一的单聚体.     

Amino Acid and Poly(Ethylene Glycol) Based Self-Organizing Polymeric Systems: Chemo-Enzymatic Synthesis and Characterization

A chemo/regio selective enzymatic methodology has been designed to synthesize amphiphilic copolymers based on amino acid diesters and poly(ethylene glycol) [PEG]. The condensation polymerization was catalyzed by immobilized Candida antarctica lipase B (Novozyme 435) under solvent-less conditions. The synthesized polymers 3a–c were derivatized with long chain acid chlorides by chemical acylation to get the amphiphilic polymers 4a–c. The physical properties of the synthesized amphiphilic polymers viz: aggregation number, critical micelle concentration (CMC), radius of gyration (R_g), hydrodynamic radius (R_h) and particle size distribution were studied by static and dynamic light scattering (SLS and DLS) techniques. The polymers were found to be promising in drug delivery applications.     

新型两亲性含糖嵌段聚合物的合成与自组装

以β-环糊精(β-CD)和2-乙基-2-噁唑啉(EtOz)为原料, 通过活性端基化学偶联法制备了乙酰麦芽七糖/聚(2-乙基-2-噁唑啉)两嵌段聚合物(AcMH-b-PEtOz), 借助核磁共振氢谱、红外光谱和凝胶渗透色谱等手段证实了产物的化学结构. 采用核磁共振氢谱、荧光光谱、透射电子显微镜、动态光散射及紫外-可见分光光度等方法探讨了产物在水溶液中的自组装行为. 结果表明, 所得嵌段聚合物直接溶于水后可通过自组装形成纳米球形“核-壳”结构胶束, 同时具有温度响应性. 所得聚合物的临界胶束浓度(cmc)为4~7 mg/L, 平均粒径(d)为83~115 nm, 临界相转变温度(LCST)为49~64 ℃, 并且均可通过PEtOz的链长进行调控.     

Fabrication and in vitro drug release study of microsphere drug delivery systems based on amphiphilic poly-alpha,beta-[N-(2-hydroxyethyl)-L-aspartamide]-g-poly(L-lactide) graft copolymers

Biodegradable amphiphilic graft copolymers with different compositions were synthesized by grafting poly(L-lactide) (PLLA) sequences onto a water-soluble poly-alpha,beta-[N-(2-hydroxyethyl)-L-aspartamide] (PHEA) backbone. The critical micelle concentration (CMC) of the graft polymers was determined by fluorescence probe technique. Using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, the graft polymers were proved to have low cytotoxicity. Based on the specific physicochemical property of the graft copolymers, submicron sized microsphere drug delivery systems were prepared by a very convenient "ultrasonic dispersion method", which did not involve toxic organic solvents. The drug-loaded microspheres had a regular spherical shape with a narrow size distribution. A hydrophobic drug, prednisone acetate, was encapsulated into polymeric microspheres and the in vitro drug release was studied.     

Thermally responsive polymeric micellar nanoparticles self-assembled from cholesteryl end-capped random poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide): synthesis, temperature-sensitivity, and morphologies

Cholesteryl end-capped thermally responsive amphiphilic polymers with two different hydrophobic/hydrophilic chain-length ratios were synthesized from the hydroxyl-terminated random poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) and cholesteryl chloroformate. The hydroxyl-terminated precursor polymers with narrow molecular weight distributions were synthesized by free-radical polymerization using 2-hydroxyethanethiol as a chain-transfer agent. The aqueous solutions of the cholesteryl end-capped copolymers exhibited reversible phase transitions at temperatures slightly above human body temperature, with the lower critical solution temperature values being 37.7 and 38.2 degrees C, respectively. The critical micelle concentration values of the two cholesteryl end-capped polymers were 9 and 25 mg/L, respectively. Polymeric micellar nanoparticles were prepared from the amphiphilic polymers using a dialysis method as well as a direct dissolution method. Transmission electron microscope studies showed that the micellar nanoparticles existed in different morphologies, including spherical, star-like, and cuboid shapes. Pyrene as a model hydrophobic compound could be readily encapsulated in these polymeric nanoparticles, at loading levels of 1.0 and 0.8 mg/g for the two cholesteryl end-capped polymers, respectively. The temperature sensitivity and unusual morphology of these novel polymeric nanoparticles would make an interesting drug delivery system.     

Arylidene Polymers. V. Synthesis,Characterization, and Thermal Studies of New Polydibenzylidenecyclopentanonehydrazides Containing Aliphatic,Aromatic, Azo,Azomethine, and Thianthrene Moieties

A new [(2-oxo-l,3-cyclopentanediylidene)bis(methylidyne-p-phenyleneoxy)]diacetic acid dihydrazide III has been prepared via interaction of 2,5-bis(p-hydroxybenzylidene) cyclopentanone I with ethyl chloroacetate in basic medium to give diester II, followed by hydrazinolysis with hydrazine. The synthesized compounds were confirmed by IR, NMR, and elemental analyses. Unreported poly-hydrazides by the low temperature interfacial polycondensation technique of III with adipoyl, sebacoyl, 4,4′-diphenic, isophthaloyl, terephthaloyl, 4,4′-azodibenzoyl, 3,3′-azodibenzoyl, 4,4′[1,4-phenylene-bis(methylidynenitrilo)]dibenzoyl dichlorides, and 2,7-dichloroformylthianthrene-5,5′,10,10′-teraoxide were prepared. In order to characterize the polymers, a model compound was synthesized from III and benzoyl chloride. The resulting polyhydrazides were confirmed by IR, UV, viscometry, DSC measurements, and thermogravimetric analysis. The crystallinities of all polyhydrazides were investigated by x-ray analysis. The effect of the nature of different moieties on the properties of these polyhydrazides was explored by comparing their physical, spectral, thermal, and x-ray analysis data.     

PAA-g-PVAc Amphiphilic Graft Copolymer Synthesized by Atom Transfer Radical Polymerization

A new amphiphilic graft copolymer containing hydrophilic poly(acrylic acid) backbone and hydrophobic poly(vinyl acetate) side chains was synthesized via sequential atom transfer radical polymerization (ATRP) followed by selective hydrolysis of poly(methoxymethyl acrylate) backbone. Grafting‐from strategy was employed to synthesize PMOMA‐g‐PVAc graft copolymer (M_w/M_n=1.64) via ATRP. The final PAA‐g‐PVAc amphiphilic graft copolymer was obtained by selective acidic hydrolysis of PMOMA backbone in acidic environment without affecting the side chains. The critical micelle concentrations (cmc) in aqueous media were determined by a fluorescence probe technique. The micelle morphologies were found to be spheres.     

Interfacial polycondensation reactions of the new monomer 1,1′-bis(β -aminoethyl)ferrocene

Condensation polymerizations of several ferrocenecontaining monomers have been investigated, using low temperature interfacial and solution techniques. 1, 1′-bis(β-aminoethyl)ferrocene was synthesized via a 6-step process starting with ferrocene. This monomer was then copolymerized with various aromatic and aliphatic diacid chlorides as well as with diisocyanates, leading to ferrocene-containing polyamides and polyureas having moderately high to low viscosities. Using the interfacial method, film formation occurred for the polyamides. The related monomer 1,1′-bis(β-hydroxyethyl)ferrocene reacted with diacid chlorides and diisocyanates to form ferrocenecontaining polyesters and polyurethanes, respectively, using the solution method. The ferrocenecontaining condensation polymers were characterized by IR spectroscopy and examined for possible liquid crystalline behavior.     

Methylene-bridged aromatic polyesters. Synthesis,characterization, and radiation-induced crosslinking

Aromatic polyesters connected by methylene groups were synthesized. Two pairs of aromatic diacid chlorides, 3,3′-methylenedibenzoyl chloride and 4,4′-methylenedibenzoyl chloride were each polymerized via interfacial polycondensation with 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 3,3′-methylenediphenol, and 4,4′-methylenediphenol. For comparison, 3,3′-carbonyldibenzoyl chloride and 4,4′-carbonyldibenzoyl chloride were similarly polymerized with bisphenol A. Substitution of meta,meta' oriented phenylene groups for para,para' oriented phenylene groups had a significant and cumulative effect in reducing the glass transition temperatures of the polymers, thereby enhancing their processability. In air the methylene groups of the polyesters undergo oxidation and crosslinking at elevated temperatures. Electron beam irradiation of thin films of the methylene-linked polyesters at room temperature resulted in some chain extension and crosslinking, as evidenced by increased solution viscosity and gel formation. Irradiation at a temperature near or above the glass transition temperatures of the polymers greatly enhanced the tendency for the polymers to crosslink.     

Synthesis of New Amphiphilic Comb-Like Copolymers Based on Maleic Anhydride and α-Olefins

Summary: Novel amphiphilic comb-like poly(α-olefin-co-maleic anhydride) with a controlled ratio of hydrophilic (polyoxyethylene) and hydrophobic (polymethylene) side chains have been synthesized and characterized. The comb-like copolymers are soluble in organic and aqueous media and form micelles whose behaviour could be correlated to the chemical structure of polymers. We foresee that amphiphilic properties of the novel comb-like polymers are obviously the basis of new architectures in solution which could be used in a broad range of applications. Using micelles from these copolymers, silver nanoparticles with a narrow particle size distribution have been obtained as stable dispersion in both polar and non-polar media.     

规整链球型含C_(60)聚苯乙烯的亲水化修饰及其在水中的自组装

C60作为碳的第三种同素异型体,一经发现就为当今科学研究所关注.其独特的光学,电学性能吸引了许多化学工作者的不懈努力,以探索其在化学、材料科学等领域的应用.精确的化学修饰不仅是改善其较差的溶解和加工性能的主要途径之一,而且更能提供规整的结构,以利于对其性能的深入研究.     

Synthesis and Characterization of Poly(ether ether ketone)s with (2,5‐dihydroxy)phenyl Side Group

A new monomer, (2,5‐dimethoxy)phenylhydroquinone (DMPH), was prepared in a two‐step synthetic procedure. One aromatic poly(ether ether ketone)s with 2,5‐dimethoxy phenyl side group (DMP‐PEEK) was synthesized via an aromatic nucleophilic substitution reaction with 4,4′‐difluorobenzophenone (DFB). Poly(ether ether ketone)s with 2,5‐dihydroxy phenyl side group (DHP‐PEEK) was obtained via hydrolysis of methoxy group on the DMP‐PEEK. Both of the high molecular weight polymers could be obtained despite the steric effect of the bulky pendant groups. The two polymers have good solubility at room temperature.     

Amphiphilic mesogen‐jacketed liquid crystalline polymers: Design,synthesis, and self‐assembly behaviors

We synthesized a series of amphiphilic mesogen‐jacketed liquid crystalline (LC) polymers with a biphenyl side‐chain mesogen containing a carboxylic acid group on one side and an octyloxy group on the other, and the number of methylene units between the biphenyl core and the exterior carboxylic acid group was varied to adjust the mesophases and the amphiphilic nature. The polymers were obtained through conventional radical polymerizations and characterized by a combination of different techniques such as thermogravimetric analysis, differential scanning calorimetry, polarized light microscopy, and X‐ray scattering. The results revealed that the polymer without any methylene spacer, POBP‐0C, did not exhibit LC properties while POBP‐1C (n = 1) and POBP‐7C (n = 7) formed double layer smectic A (S_A) phases. The hydrogen bonding among the carboxylic acid groups and the segregation between the carboxylic acid groups and the alky chains played important roles in forming the mesophases. In addition, the solution self‐assembly behaviors were also preliminarily investigated through the fluorescent probe technique and transmission electron microscopy, and vesicles with uniform sizes were observed. The weak hydrophilicity and large degree of freedom of the carboxylic acid group and the relative rigidity of the polymer chain due to the “jacketing” effect were responsible for the formation of the structures. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Amphiphilic comb-like polymers based on poly(oxyethylene)s as drug-delivery carriers

Comb-like polymers with biocompatible oxyethylene backbones and amphiphilic side groups were synthesized via polymer-analogous reactions. Using these polymers, indomethacin-loaded polymeric micelles were fabricated with various drug-to-polymer weight ratios using the oil-in-water emulsion technique. In addition, the size, size distribution, CMC, drug-loading content, and entrapment efficiency of the polymeric micelles were analyzed. The volume-weighted diameters of polymeric micelles ranged from 10 to 140 nm and were narrowly distributed for passive targeting drug delivery. The CMCs were lower (approximately 10(-8) M) than for conventional surfactants and block copolymers.     

含3,4-乙撑二氧取代基的聚三噻吩衍生物的合成与表征

通过Stille反应合成了3,′4′-乙撑二-氧2,2′∶5,′2″-三噻吩,并以其作为单体,在0~5℃下,以FeCl3为氧化剂,在氯仿溶液中合成了3种聚(3,′4′-乙撑二氧-2,2′∶5,′2″-三噻吩)。并采用紫外-可见光谱(UV-Vis)、傅里叶红外光谱(FT-IR)、凝胶色谱(GPC)、循环伏安(CV)、透射电镜(TEM)和热重分析(TGA)对聚合物进行了表征。同时讨论了乙撑二氧取代基和FeCl3用量对聚合物性质的影响。结果表明:聚合物的紫外最大吸收为466~474 nm,数均分子量为3.4×103~3.6×103,能隙大约为2.05 eV,热分解温度为110℃。     

Properties of dendronized acrylic polymers: Effect of composition and structure of peripheral groups

Two series of new acrylic polymers carrying L-aspartic acid-based dendrons in side chains with terminal hexyloxycarbonyl groups that are both directly and indirectly, via a rigid spacer, attached to polymer chains have been synthesized by the free-radical polymerization of monomers. The polymerization ability of the monomers has been studied. The properties of new polymers are compared with the properties of polymer analogs containing terminal methoxycarbonyl groups of dendrons. Upon incorporation of the rigid spacer, the shielding of reactive centers decreases and the polymerizability of the monomers increases. The replacement of terminal methyl groups in dendrons with hexyl groups in spacer-free polymers leads to a reduction in the degree of polymerization, while in the case of polymers containing spacers, high-molecular-mass products arise. This phenomenon is facilitated by the amphiphilic nature of the polymers and the additional enhancement in the rigidity of chains. A polymer carrying a third-generation dendron has been synthesized only for the latter series.     

Synthesis,Characterization and Thermal Properties of Imide-Containing Phthalonitrile Polymers

A series of novel imide-containing phthalonitrile polymers with flexible aryl ether units have been synthesized and characterized. Bisphenol monomers were synthesized by a multi-step synthesis involving a condensation reaction between aromatic aldehydes and 2,6-dimethyl phenol, respectively. The bisphenols obtained were reacted with 4-nitrophthalonitrile to form aryl ether linkage containing bisphthalonitriles. These products were hydrolyzed to tetra carboxylic acid, which were subsequently converted into corresponding dianhydrides. The obtained dianhydrides were reacted with synthesized 4-(4′-aminophenoxy) phthalonitrile by thermal imidization leading to the formation of imide-containing phthalonitrile monomers. The synthesized monomers were cured with 3.5 wt% of aromatic diamine, 4,4′-diaminodiphenylsulphone(DDS). The structure and properties of all compounds synthesized were confirmed by using elemental analysis, FT-IR, ¹H-NMR, ¹³C-NMR, DSC, TGA and rheometric studies. The cure temperatures are found to be in the range of 283–302°C, the temperature of 5% and 10% weight loss from TGA are in the range of 433–492°C in N₂ and 424–478°C in air, char yield at 800°C is 40–51%.