Supramolecular polymers having chiral interactions

Poly(L-glutamate) having amphiphilic side chains was designed as membrane materials for optical resolution of α-amino acids. Solvent-cast films of the poly(glutamate) (PLG) had a self-ordered structure containing α-helix of the poly(L-glutamate). Optical resolutions of various amino acids were carried out through the thin membranes of the amphiphilic poly(L-glutamate). Racemic mixtures of Tryptophan were completely separated through the membrane. Mechanism of the optical resolutions was investigated in terms of molecular recognitions of racemic Tryptophan by the ordered structure of the membrane. Polymers having pendant PLG and α-amino acids were synthesized and their permeation behaviors were investigated.     

两亲性聚(L-谷氨酸γ-苄基酯)-聚乙二醇接枝共聚物的自组装行为和载药性能研究

由氨基酸及其衍生物聚合形成的聚肽,因其独特的结构和性能,近年来在蛋白质结构模拟、分子链构象研究、生物医学等领域备受关注．其中两亲性聚肽共聚物的自组装行为,为开发具有生物相容性、可控释、可降解性的新型药物载体创造了条件．目前对聚肽共聚物自组装及载药性能研究主要集中于聚肽嵌段共聚物胶束,     

Chromatographic resolution of dipeptide enantiomers and diastereomers on chiral stationary phases from poly(L-leucine) or poly(L-phenylalanine)

Two types of chiral stationary phase, polymer-bonded and non-bonded, containing poly(L-leucine) and poly(L-phenylalanine) were prepared. These stationary phases gave higher enantioselectivity for the optical resolution of various derivatives of leucylphenylalanine methyl ester by liquid chromatography than did poly(L-alanine) and poly(L-glutamate).     

两亲性共聚物的分子设计与合成及其共混膜性能

从分子结构设计出发,采用自由基聚合、醚化、酯化、原子转移自由基聚合(ATRP)、可逆加成断裂链转移自由基聚合(RAFT)等方法合成了一系列具有不同分子结构(包括接枝、嵌段、交替、超支化等)和链形态(包括直链、梳状、哑铃状、链球状等)的两亲性共聚物,并对这些聚合物进行了谱学表征和性能测试.将这些两亲性共聚物与聚合物膜材料(包括聚偏氟乙烯、聚氯乙烯、聚砜、聚醚砜、聚醚砜酮等)进行溶液共混,通过相转化法制备共混膜,在成膜热力学和动力学分析的基础上,对共混膜的结构和性能进行调控.研究发现,两亲性共聚物在成膜过程中自发地向膜表面迁移富集,并进行自组装,在膜表面形成两亲性共聚物包膜,显著改善了聚合物多孔膜的亲水性和抗污染性能.此外,两亲性共聚物中的功能基团还可赋予共混膜某些功能特性,如生物相容性、环境响应性(pH、温度敏感性)、酶活性等.     

alpha-Helical polypeptide microcapsules formed by emulsion-templated self-assembly

alpha-Helical peptide microcapsules were prepared by the emulsion-templated self-assembly of amphiphilic poly(gamma-benzyl L-glutamate)s (PBLG) 1. By mixing solutions of 1 in dichloromethane (in the form of a sodium salt) with water, oil-in-water emulsions were obtained. Spontaneous stripping of the dichloromethane phase caused a decrease in the diameter of the microdroplets and finally stable microcapsules formed. The microcapsules contain an inner aqueous phase as observed by confocal laser scanning microscopy (CLSM). Binding of hydrophobic pyrene molecules to the polypeptide shell was also demonstrated. The present polypeptide microcapsules are stable even after drying in air and they would serve as supramolecular vehicles for both hydrophobic and water-soluble molecules.     

含氟两亲接枝共聚物的制备及其结晶行为

采用大分子单体技术合成了一系列以聚乙二醇为支链、甲基丙烯酸六氟丁酯为主链的含氟两亲接枝共聚物(PHFMA-g-PSPEG)。用1HNMR和凝胶色谱(GPC)对制备的大分子单体和两亲接枝共聚物的结构进行了表征。利用示差扫描量热法(DSC)、X射线衍射(XRD)和偏光显微镜(POM)测试技术对含氟两亲接枝共聚物的结晶行为进行了研究。DSC和XRD结果表明,随着共聚物中含氟链段质量分数的增加,其结晶温度(Tc)和结晶度(Xc)均降低,而结晶熔融温度(Tm)先减小后增加。POM发现,随着共聚物中含氟链段质量分数的增加,其结晶速度减慢,共聚物形成清晰球晶的能力减弱,当共聚物中含氟链段质量分数为57%时,含氟两亲接枝共聚物已不能形成清晰的球晶。     

Photo‐responsive amphiphilic poly(α‐hydroxy acids) with pendent o‐nitrobenzyl ester constructed via copper‐catalyzed azide‐alkyne cycloaddition reaction

Photo‐responsive block copolymer mPEG‐b‐poly(Tyr)‐g‐NB was prepared by introduction of o‐nitrobenzyl ester group into the side chain of amphiphilic poly(ethylene glycol)‐b‐poly(α‐hydroxy acids) (mPEG‐b‐poly(Tyr)) containing pendent alkynyl group via copper‐catalyzed azide‐alkyne cycloaddition reaction. The amphiphilic mPEG‐b‐poly(Tyr) was synthesized via the ring‐opening polymerization of O‐carboxyanhydrides, with monomethoxy poly(ethylene glycol) (mPEG) as macroinitiator. The molecular structure, self‐assembly, and photo‐controlled release of the obtained mPEG‐b‐poly(Tyr)‐g‐NB were thoroughly investigated. mPEG‐b‐poly(Tyr)‐g‐NB could self‐assemble into spherical micelles in water and showed disassembly under UV light irradiation, which was demonstrated by means of UV‐vis spectroscopy, scan electron microscopes, and dynamic light scattering measurement. Fluorescence emission measurements demonstrated that Nile red, encapsulated by micelles, can be released upon UV irradiation. This study provides a convenient way to construct smart poly(α‐hydroxy acids)‐based nanocarriers for controlled release of hydrophobic drugs. Copyright © 2015 John Wiley & Sons, Ltd.     

Thermoresponsive nanostructures by self-assembly of a poly(N-isopropylacrylamide)-lipid conjugate

The synthesis and purification of a poly(N-isopropylacrylamide)-lipid conjugate and its use in the preparation of a thermoresponsive lipid mesophase is described. Specifically, poly(N-isopropylacrylamide) with a single carboxyl group at one end was activated with dicyclohexylcarbodiimide/N-hydroxysuccinimide to form an active ester. This N-hydroxysuccinimide ester was then used to form a dimyristoyl-sn-glycero-3-phosphoethanolamine conjugate with poly(N-isopropylacrylamide) via an amide bond, rendering the conjugate amphiphilic. Quaternary phases comprising the conjugate, a phosopholipid, dimyristoylphosphatidylcholine, and a cosurfactant, N,N-dimethyldodecylamine-N-oxide, dispersed in water were found to self-assemble at room temperature to form liquid crystalline gels, adopting an expanded lamellar structure. A modest increase in temperature triggered the reversible conversion of the aggregate to a collapsed lamellar structure, while a modest reduction in temperature resulted in its conversion to a nonlamellar phase. The phases were characterized by polarized optical microscopy and small-angle X-ray scattering (SAXS).     

Supramolecular helical assembly of an achiral cyanine dye in an induced helical amphiphilic poly(phenylacetylene) interior in water

A water-soluble amphiphilic poly(phenylacetylene) bearing the bulky aza-18-crown-6-ether pendants forms a one-handed helix induced by l- or d-amino acids and chiral amino alcohols through specific host-guest interactions in water. We now report that such an induced helical poly(phenylacetylene) with a controlled helix sense can selectively trap an achiral benzoxazole cyanine dye among various structurally similar cyanine dyes within its hydrophobic helical cavity inside the polymer in acidic water, resulting in the formation of supramolecular helical aggregates, which exhibit an induced circular dichroism (ICD) in the cyanine dye chromophore region. The supramolecular chirality induced in the cyanine aggregates could be further memorized when the template helical polymer lost its optical activity and further inverted into the opposite helicity. Thereafter, thermal racemization of the helical aggregates slowly took place.     

Protonation and diffusion phenomena in poly(4-vinylpyridine)-based weak anion-exchange membranes

Purification and concentration of mineral acids can be carried through dialysis processes with anion-exchange membranes. Weak anion-exchange membranes are active only for sufficient acid concentrations in their structure, however too high concentrations result in significant proton leakage, i.e. reduction in the transport selectivity. The present paper deals with the kinetics of acid diffusion through two commercial poly(4-vinylpyridine)-based weak anion-exchange membranes which comprises protonation of the exchanging groups. The electrical conductivity and the water content of the membranes were shown to be linear function of the protonation degree of poly(4-vinylpyridine) groups. Kinetics of protonation and diffusion of acids have been investigated using dialysis cells. First diffusion kinetics has been studied in a conventional dialysis cell, by observation of the transient acid transport through the membrane (macroscopic studies). Besides, protonation kinetics was investigated using a miniaturised dialysis cell coupled to confocal Raman microspectrometer. Profiles of non-protonated and protonated sites in the membrane were recorded along time, depending on the membrane grade and the nature of the acid transported. Interpretation of the two sources of data yielded permeability coefficient and diffusion coefficient, whose meaning is discussed. A mechanism for protonation/diffusion in this type of weak anion exchangers in acidic media was proposed.     

Synthesis and characterization of amphiphilic antibacterial copolymers

Macromolecule antimicrobials have been explored in foundational research and practical application due to their potential merit for reducing the residual toxicity, increasing their efficiency, selectivity, and prolonging the lifetime of the antimicrobial material. In this work, the quaternized poly(styrene)‐b‐poly(DMAEMA) diblock polymers are synthesized by reversible addition‐fragmentation chain transfer polymerization (RAFT). The minimum inhibitory concentration (MIC) evaluation and optical density (OD) method demonstrated that the amphiphilic antibacterial biomaterials have exceptional antibacterial properties. The amphiphilic polycation has an admirable antibacterial property, and these quaternized diblocks are potent biocides and nonhemolytic. The relationship between the structure and activity is discussed with respect to molecular weight of the diblocks and bacteria structural dependence. Copyright © 2011 John Wiley & Sons, Ltd.     

Self-assembly of amphiphilic liquid crystal polymers obtained from a cyclopropane-1,1-dicarboxylate bearing a cholesteryl mesogen

We study the self-assembly of a new family of amphiphilic liquid crystal (LC) copolymers synthesized by the anionic ring-opening polymerization of a new cholesterol-based LC monomer, 4-(cholesteryl)butyl ethyl cyclopropane-1,1-dicarboxylate. Using the t-BuP(4) phosphazene base and thiophenol or a poly(ethylene glycol) (PEG) functionalized with thiol group to generate in situ the initiator during the polymerization, LC homopolymer and amphiphilic copolymers with narrow molecular weight distributions were obtained. The self-assemblies of the LC monomer, homopolymer, and block copolymers in bulk and in solution were studied by small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and transmission electron microscopy (TEM). All polymers exhibit in bulk an interdigitated smectic A (SmA(d)) phase with a lamellar period of 4.6 nm. The amphiphilic copolymers self-organize in solution into vesicles with wavy membrane and nanoribbons with twisted and folded structures, depending on concentration and size of LC hydrophobic block. These new morphologies will help the comprehension of the fascinating organization of thermotropic mesophase in lyotropic structures.     

Synthesis and characterization of polyimide containing PEG/PDMS amphiphilic conetworks by hydrosilylation: Correlation between structure and properties

Soluble poly(imide‐siloxane)s were obtained by carefully designing the synthesis and introducing poly(ethylene glycol) (PEG) units, thereby making the system amphiphilic in nature. The solubility of the synthesized PEG containing poly(mide‐siloxane)s (PPIS) in various solvents was tested and their thermal properties were investigated. Polymeric siloxane networks were prepared by combining imide groups and hydrophilic PEG components with sufficient variability in their composition to analyze their physicochemical details. The amine groups of the imides were varied in their rigidity and bulkiness, and their effect on the mechanical and thermal properties was studied. Here we have also examined the surface property of the networks through contact angle measurements, morphology through SEM, existence of amorphous nature by WAXD, and their structure–property relationships were correlated. The thermal analysis revealed the phase separation of the three components poly(dimethyl siloxane) (PDMS), PEG, and imide, showing a tricomponent amphiphilic conetworks. The mechanical properties were found to be improved by the phase separated PPIS containing more rigid imide groups. The overall properties of the amphiphilic conetwork has the features of differing hydrophilicity, mobility, and morphology distributed across a matrix, which has a microphase separated design suitable for gas separation and biomedical applications. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1707–1726, 2007     

Study of emulsion polymerization stabilized by amphiphilic polymer nanoparticles

Submicron-sized polystyrene (PS) microspheres with a relatively narrow particle size distribution can be easily produced through emulsion polymerization induced by γ-ray at room temperature using a new type of amphiphilic cross-linked poly(stearyl methacrylate-co-acrylamide-co-acrylic acid) particles as stabilizer. The properties of these amphiphilic particles were described, including morphology, size, ζ potential, and contact angles. The effect of the pH value and the content of amphiphilic particles on the formation and stability of emulsions were also investigated. Meanwhile, the obtained PS microspheres were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. In addition, through observing the morphology and size of emulsion droplets at different times under an optical microscope, we found it is interesting that Pickering emulsions formed initially disappeared gradually, which is different from the common Pickering emulsions stabilized by inorganic particles. Thus, the mechanism was further discussed.     

聚(L-谷氨酸γ-苄酯)-聚四氢呋喃-聚(L-谷氨酸γ-苄酯)三嵌段共聚物的合成与表征

聚氨基酸是一类低毒性、生物相容性良好、易被机体吸收和代谢的可降解合成高分子材料，在药物控释载体、组织工程支架、生物材料表面改性方面得到了广泛应用．但其降解周期及降解速度通常难以控制，应用受到一定限制．通过共聚方法将生物相容和亲水性良好的聚乙二醇（PEG）引入聚氨基酸链段中形成两亲性嵌段共聚物旧，研究其自组装行为，及作为基因转染和药物控释载体等已成为高分子科学领域新的研究热点．     

Self-assembly and luminescence of oligo(p-phenylene vinylene) amphiphiles

We have synthesized a series of amphiphilic molecules consisting of oligo(phenylene vinylene) (OPV) asymmetrically end-substituted with a hydrophilic poly(ethylene glycol) (PEG) segment and a hydrophobic alkyl chain. This amphiphilic structure induces self-assembly into both thermotropic and lyotropic lamellar liquid crystalline (LC) phases. The molecules form strongly fluorescent, self-supporting gels in both water and polar organic solvents, even at high concentrations on the order of 30 wt %. These self-assembled structures have been characterized by small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), and polarized optical microscopy (POM). Photoluminescence (PL) is influenced by the structure of the material, with enhanced emission in the LC state due to assembly of the chromophore in confined two-dimensional layers. Self-assembly controlling molecular aggregation at the nanoscale could significantly improve the performance of OPV-based materials in optoelectronic devices.     

多功能两亲梳状聚合物的合成及包覆荧光量子点

利用溶液聚合和成酰胺反应合成了多功能梳状两亲性共聚物,聚(甲基丙烯酸-co-甲基丙烯酸十八酯)-(乙醇胺-乙二胺叶酸)(PSM-EE-FA).用红外光谱(FTIR),核磁共振(1H-NMR)及凝胶渗透色谱(GPC)表征了该聚合物的结构及分子量分布.实验结果证明合成了该聚合物,其数均分子量(Mn)为28600,多分散性为1.375.用该两亲梳状聚合物包覆油溶性CdSe/ZnS量子点,通过相转移作用,得到水溶性靶向量子点(PSM-EE-FA-QDs).该水溶性量子点溶液具有较好的稳定性.通过紫外-可见(UV-Vis)及荧光发射光谱分析对该量子点的光学性质进行研究.结果表明,PSM-EE-FA-QDs的紫外-可见光谱及荧光发射光谱峰形与原量子点基本一致.由于量子点表面聚合物层的形成,峰位发生少量红移.该量子点水溶液的荧光强度是原量子点氯仿溶液的98%,荧光产率是原量子点氯仿溶液的95%.动态光散射(DLS)及透射电镜(TEM)测试结果表明水溶性量子点分布均匀.合成的水溶性量子点不但光学性能稳定,而且聚合物及水溶性量子点的合成方法较为简便.     

Amphiphilic Comb‐Like Poly(oxyethylene) and Its Complexes with LiClO4: Synthesis and Mesomorphic Behavior

Summary: We prepared an amphiphilic, comb‐like poly(oxyethylene) containing decyl‐tri(oxyethylene) amphiphiles in the side chain using a polymer analogous reaction to obtain a novel nonionic amphiphilic polymeric system with high molecular weight. The amphiphilic comb‐like poly(oxyethylene) itself only showed a side‐chain crystalline phase below its melting temperature of −31 °C. When the polymer was mixed with lithium perchlorate, a smectic liquid‐crystalline phase appeared. The ordered phases of the polymer and the polymer mixture were studied by differential scanning calorimetry, polarized optical microscopy, and X‐ray diffraction.

POM image (200 X) of D3OTP1 at room temperature.     

Solubilities of polypeptides with hydrophobic and negatively charged side-chains into cationic artificial membrane vesicles

The influence of relatively low molecular weight polypeptides on the structure of membrane vesicles composed of distearyldimethylammoniumchloride (DSACl) was investigated by means of calorimetric, fluorescence spectroscopic and fluorescence polarization measurements, and correlated with the degree of hydrophobicity and/or dissociation of the polypeptide side chains. The polypeptides used were poly(-methyl L-glutamate) (PMLG,M _v =4400), copoly(methyl L-glutamate L-glutamic acid) containing 20 mol % of L-glutamic acid (80/20 MG/GA,M _v =4200) and poly(L-glutamic acid) (PLGA,M _v =9200). The hydrophobic polypeptide, PMLG, was readily incorporated into the DSACl membrane vesicles to form membrane-spanning helices, resulting in a decrease in the microviscosity of the hydrophobic region of the membrane phase. The partially charged hydrophobic polypeptide, 80/20 MG/GA, was almost insoluble into the membrane below the phase transition temperature of the DSACl vesicle,T _c 40.4 °C, however, the solubility of the copolymer into the membrane was drastically increased aboveT _c . The negatively charged polypeptide, PLGA, can hardly penetrate through the membrane vesicle and formed crosslinking between the positively charged DSACl vesicles. It was also confirmed that aggregation or clustering of the hydrophobic PMLG-helices progressed in the membrane phase belowT _c .     

SYNTHESIS AND CHARACTERIZATION OF POLY(AMINO ACID-UREA)S COMPRISING NOVEL TRIBLOCK COPOLYMERS OF POLY(TETRAHYDROFURAN) AND POLY(γ-BENZYL L-GLUTAMATE)S

A kind of novel triblock copolymers of poly(γ-benzyl L-glutamate)-b-poly(tetrahydrofuran)-b-poly(γ-benzyl L-glutamate)s(PBLG-b-PTHF-b-PBLG)was synthesized by using bis(3-aminopropyl)terminated polytetrahydrofuran to initiate the ring-opening polymerization ofγ-benzyl L-glutamate N-carboxyanhydride(BLG-NCA).The corresponding multiblock poly(amino acid-urea)s were prepared in one-pot protocol from the chain extension of PBLG-b-PTHF-b-PBLG with MDI.The resulting triblock and multiblock copolymers were chara...