Synthesis and characterization of H-type amphiphilic liquid crystalline block copolymers by ATRP

H-type amphiphilic liquid crystalline block copolymers containing azobenzene were synthesized by atom transfer radical polymerization （ATRP）. Macroinitiators prepared by the esterification between poly（ethylene oxide） （PEG） and 2,2-dichloroacetyl chloride were utilized to initiate the polymerization of 6-[4-（4-ethoxyphenylazo）phenoxy]hexyl rnethacrylate （M6C）. The resulting macroinitiators and block copolymers were characterized by ^1H NMR, gel permeation chromatography （GPC）. Polarizing optical microscopy （POM） and differential scanning calorimetry （DSC） preliminarily revealed the liquid crystalline property of these block copolymers. This series of liquid crystalline block copolymers are promising in some areas, such as optical data storage, optical switch, and molecular devices.

CONTROLLED SYNTHESIS OF AMPHIPHILIC BLOCK POLYMERS HAVING GLUCOSE RESIDUES AND THEIR STRUCTURE FORMATION

Vinyl ether (VE)-based amphiphilic block copolymers with D-glucose residues as hydrophilicpendants were synthesized by CH_3 CH(OiBu)Cl/ZnI_2-initiated sequential living cationic copolymerization of3-O-(vinyloxy)ethyl-1, 2:5, 6-di-O-isopropylidene-D-glucofuranose (IGVE) and isobutyl VE (IBVE ) andsubsequent deprotection. The precursor block copolymers had a narrow molecular weight distribution(M_w/M_n～1.1) and a controlled segmental composition. The solubility characteristics of the amphiphiliccopolymer depended strongly on composition. Their solvent-cast thin films were examined, under atransmission electron microscope, and could be seen to exhibit various microphase-separated surfacemorphologies such as spheres, cylinders, and lamellae, depending on composition. The amphiphiliccopolymers with the appropriate segmental composition were found to form a stable monolayer at the air-water interface, which was successfully transferred onto a substrate by the Langmuir-Blodgett (LB)technique. The layered strucfure of the built-up LB films was controlled by blending the homopolymer.

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.

MORPHOLOGICAL TRANSITION BETWEEN VESICLES AND TUBULES FOR A GLYCOPOLYMER-CONTAINING AMPHIPHILIC DIBLOCK COPOLYMER IN AQUEOUS SOLUTIONS

The morphological transition of molecular assemblies in aqueous solutions for a new amphiphilic diblock copolymer induced by changing the initial solvent conditions was studied by transmission electron microscopy (TEM). The copolymer was polystyrene(77)-b-poly[2-(beta -D-glucopyranosyloxy)ethyl acrylate (6)] (PSt(77)-b-PGEA(6)) and the solvent was a mixture of DMF and THF. PSt(77)-b-PGEA(6) yields vesicles and tubules when it is initially dissolved in THF and DMF respectively. The morphological transition between vesicles and tubules can be achieved by simply varying the amounts of THF and DMF, or changing the temperature at which the aggregates were prepared.

Preparation of Nano-porous Materials(Ⅱ) by Cross-linking of Amphiphilic Self-assemblies

Amphiphilic block copolymers can exhibit rich and complex morphologies in aqueous solutions, but these structures are usually delicate, easily disturbed by composition change or temperature change. In this work, the use of different methods to cross link block copolymer self assemblies in the presence of a selective solvent and to stabilize the structures is reviewed. In addition, the cross linking reaction kinetics of block copolymer amphiphilic self assemblies is briefly discussed.

Metal-free synthesis of amphiphilic functional polycarbonates

Amphiphilic block copolymers of poly（5-benzyloxy trimethylene carbonate） （PBTMC） and poly（ethylene glycol） （PEG） were synthesized through enzymatic polymerization using immobilized porcine pancreas lipase （IPPL）. The obtained copolymers with different compositions were characterized by GPC and IH NMR. The copolymer composition was in agreement with the feed ratio. The molecular weight of the copolymers showed an increasing trend with the decrease of PEG contents. MiceUes of the copolymers were formed by dialysis procedure, and characterized by transmission electron microscopy （TEM）.

Influence of Block Copolymer on Formation and Acid Resistant Properties of Hybrid CaCO_3 Particles

Block copolymer polystyrene-b-poly（acrylic acid）（PS-b-PAA） was used as structural template for the synthesis of CaCO3 microparticles. Through this procedure, acid resistant hybrid CaCO3 micro- spheres were obtained. Acid resistant properties of this type of hybrid CaCO3 were studied. Size measurement shows that the acid resistant properties of the hybrid particles are different in different solutions, such as HCl, EDTA, and H2SO4 solutions.

SYNTHESIS OF POLYBUTADIENE MACROINITIATOR AND POLYBUTADIENE/POLYACRYLAMIDE BLOCK COPOLYMERS

An azo-group containing polybutadiene macroinitiator was prepared by Pinner synthesis and characterized by IR, NMR, GPC, viscosity and elemental measurements. The macroinitiator was further use to polymerize acrylamide (AAm) in benzene to form polybutadiene/polyacrylamide (PBD/PAAm) block copolymers. High conversion of AAm was obtained over a wide range of monomer/macroinitiator ratios. The PBD/PAAm block copolymers were found to have excellent solvent resistance.

An Overview of the Synthesis and Gene Transfer Properties of Triblock Copolymers Poly(2-Methyl-2-Oxazoline-b-Tetrahydrofurane-b-2-Methyl-2-Oxazoline)

The synthesis of poly(2-methyl-2-oxazoline-b-tetrahydrofurane-b-2-methyl-2-oxazoline) triblock copolymer of low molar mass has been carried out. Characterization of the purified polymer by 1H and 13C NMR spectroscopies is described. These block copolymers did not give DNA containing polyplexes. The in vivo transfection properties were investigated by injection of tibialis muscles and intratracheal administration of female Swiss mice. These triblock copolymers with a molar ratio [2-methyl-2-oxazoline units]/[tetrahydrofurane units] in the 3 - 5 range gave a higher transfection efficiency than that of Lutrol or of PE6400 which are the gold standards of this transfection technique. Hydrolysis increased the performances of muscle transfection, showing the beneficial effect of the presence of positive charges, but was clearly detrimental to the transfection efficiency of pulmonary epithelium.

Biodegradable amphiphilic block copolymers containing functionalized PEO blocks:Controlled synthesis and biomedical potentials

A series of controllable amphiphilic block copolymers composed of poly(ethylene oxide)(PEO) as the hydrophilic block and poly(ε-caprolactone)(PCL) as the hydrophobic block with the amino terminal group at the end of the PEO chain(PCL-b-PEO-NH2) were synthesized.Based on the further reaction of reactive amino groups,diblock copolymers with functional carboxyl groups(PCL-b-PEO-COOH) and functional compounds RGD(PCL-b-PEO-RGD) as well as the triblock copolymers with thermosensitive PNIPAAm blocks(PCL-b-PEO-b-PNIPAAM) were synthesized.The well-controlled structures of these copolymers with functional groups and blocks were characterized by gel permeation chromatography(GPC) and 1H NMR spectroscopy.These copolymers with functionalized hydrophilic blocks were fabricated into microspheres for the examination of biofunctions via cell culture experiments and in vitro drug release.The results indicated the significance of introducing functional groups(e.g.,NH2,COOH and RGD) into the end of the hydrophilic block of amphiphilic block copolymers for biomedical potentials in tissue engineering and controlled drug release.

Molecular dynamics study of water diffusion in an amphiphilic block copolymer with large difference in the blocks＇ glass transition temperatures

Isothermal-isobaric molecular dynamics simu- lation was used to study the diffusion mechanism of water in polyurethane-block-poly（N-isopropyl acrylamide） （PU- block-PNIPAm） with a hydrophobic PU/hydrophilic PNIPAm mass ratio of 1.4 to 1 at 298 K and 450 K. Here, the experimental glass transition temperature （Tg） of PU is 243 K while that of PNIPAm is 383 K. Different amounts of water up to 15 wt-% were added to PU-block- PNIPAm. We were able to reproduce the specific volumes and glass transition temperatures （250 K and 390 K） of PU- block-PNIPAm. The computed self-diffusion coefficient of water increased exponentially with increasing water concentration at both temperatures （i.e., following the free volume model of Fujita）. It suggested that water diffusion in PU-block-PNIPAm depends only on its fractional free volume despite the free volume inhomo- geneity. It is noted that at 298 K, PU is rubbery while PNIPAm is glassy. Regardless of temperature, radial distribution functions showed that water formed clusters with sizes in the range of 0.2-0.4 nm in PU-block- PNIPAm. At low water concentrations, more clusters were found in the PU domain but at high water concentrations, more in the PNIPAm domain. It is believed that water molecules diffuse as clusters rather than as individual molecules.

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（e-caprolactoneXPCL） 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 acidXPAA） blocks allowed the star block copolymers to further change their morphologies of aqueous aggregates m response to pH values.

Self-assembling Characteristics of Amphiphilic Star Block Copolymers with a Polyelectrolyte Shell

1 Results Amphiphilic block copolymers are capable of forming supramolecular assemblies resembling those observed in nature,such as spherical micelles,worm micelles,and vesicles.Changing the solvent composition,ionic strength or pH of the polymer solution may induce the self-assembly of block copolymers or trigger the transition between the geometries of noncovalent assemblies.In the current work,we have synthesised starlike amphiphilic block copolymers having hydrophobic poly(methyl methacrylate),PMMA,...

All-conjugated amphiphilic diblock copolymers for improving morphology and thermal stability of polymer/nanocrystals hybrid solar cells

Herein, the ability to optimize the morphology and photovoltaic performance of poly（3-hexylthiophene） （P3HT）/ZnO hybrid bulk-heterojunction solar cells via introducing all-conjugated amphiphilic P3HT-based block copolymer （BCP）, poly（3- hexylthiophene）-block-poly（3-triethylene glycol-thiophene） （P3HT-b-P3TEGT）, as polymeric additives is demonstrated. The results show that the addition of P3HT-b-P3TEGT additives can effectively improve the compatibility between P3HT and ZnO nanocrystals, increase the crystalline and ordered packing of P3HT chains, and form optimized hybrid nanomorphology with stable and intimate hybrid interface. The improvement is ascribed to the P3HT-b-P3TEGT at the P3HT/ZnO interface that has strong coordination interactions between the TEG side chains and the polar surface of ZnO nanoparticles. All of these are favor of the efficient exciton dissociation, charge separation and transport, thereby, contributing to the improvement of the efficiency and thermal stability of solar cells. These observations indicate that introducing all-conjugated amphiphilic BCP additives can be a promising and effective protocol for high-performance hybrid solar cells.

Open tubular capillary electrochromatography with block co-polymer coating for separation of β-lactam antibiotics

A new open-tubular capillary electrochromatography (OT-CEC) method for analysis of β-lactam antibiotics has been developed with unique block co-polymer coating. To obtain the highly ordered block polymer chains, reversible addition fragmentation chain transfer radical polymerization method was used to synthesize poly (maleic anhydride-styrene-N-isopropylacrylamide). The prepared block copolymer coating was characterized with NMR, fourier transform infrared spectroscopy and scanning electron microscope. Several key separation factors of OT-CEC, which including polymer amount,stability of the coating, temperature, species of organic additives, buffer pH and concentration, were investigated in detail. Our results indicated that the separation efficiency was improved greatly with the coating capillary and the three test analytes could be baseline separated. Then, the separation mechanism was briefly explored. Moreover, the proposed OT-CEC method displayed promising quantitative analysis property of the three test analytes with good linearity (R2>0.99), repeatability (relative standard deviations <0.9%) and high recovery (95.4%-106.2%). Further, the assay was applied in monitoring the three test β-lactam antibiotics (cephradine, cephalexin and amoxicillin) in serum samples, providing a useful platform for construction of novel polymer coatings in OT-CEC system and for analysis of drugs in real bio-samples.

Cooperative organizations of small molecular surfactants and amphiphilic block copolymers:Roles of surfactants in the formation of binary co-assemblies

The construction of highly ordered organizations through self-assembly is one of the most popular phenomena both in natural and artificial environments.Amphiphilic molecules are the most commonly used building blocks for the self-assembly,which are conventionally known as amphiphilic low molecular weight surfactants with polar heads and nonpolar tails,or amphiphilic block copolymers(BCPs)consisting of covalently bonded hydrophilic and hydrophobic block chains.Compared with single surfactant self-assembly system,binary amphiphiles co-assembly systems composing of both small mass surfactants and amphiphilic BCPs feature high flexibilities and versatilities in materials designing and structure regulation,ascribing to the vast possibilities of intermolecular interactions within the systems and facile component modulations during the assembly processes.The amphiphilic features of the two kinds of molecules endow them with similar self-assembly behaviors,while the unique and distinct characters of each kind of amphiphiles lead to various complex but highly diversified co-assembly systems.According to the roles of the surfactant played in the co-assembly system,in this review,we summarize the binary coassembly systems from three distinct types:1)the co-micellization system in which the surfactants are added into the BCPs assemblies as a self-assembly assistant;2)the co-emulsification system in which the surfactants work as an emulsion stabilizer to assist and confine the assembly of BCPs in 3D geometries;3)the co-templating system where the individual micelles of both surfactant and BCPs are hierarchically arranged and distributed to guide the formation of hierarchical nanomaterials.Following this,the major potential applications of the nanomaterials synthesized from the binary amphiphiles in biological field are described.Finally,we shortly discuss the current challenges and future perspectives of the binary amphiphiles selfassembly systems.

微乳液法制备水溶性双亲丙烯酰胺-苯乙烯嵌段共聚物

分别以十二烷基硫酸钠 (SDS)、壬基酚聚氧乙烯醚 (OP 10 )为表面活性剂 ,丙烯酰胺 (AM)的水溶液为连续相 ,苯乙烯 (St)为分散相 ,构成微乳液共聚合体系 ,合成了水溶性双亲嵌段共聚物 ,并通过荧光探针技术、差示扫描量热 (DSC)测试及流变性能的测定表征了共聚物的嵌段性结构 ,用红外光谱 (FTIR)及紫外光谱 (UV)

窄分布两亲性嵌段共聚物的合成及其胶束化行为研究

利用原子转移自由基聚合合成了具有两亲性的嵌段聚合物聚苯乙烯 -b-聚丙烯酸 ( PS-b-PAA) ,用FTIR,1 H NMR,SEC对其进行了表征 ,并利用荧光探针技术研究了其在水溶液中的胶束化行为 .进一步的研究表明 。

含两亲性PEO-b-PBA增容剂的吸水膨胀橡胶的制备及性能

以天然橡胶为基体 ,微米级交联聚丙烯酸钠为高吸水性树脂 ,两亲性嵌段共聚物聚氧化乙烯 - b-聚丙烯酸丁酯 (PEO- b- PBA)为增容剂 ,聚乙二醇为吸水促进剂 ,制备了嵌段共聚物增容型吸水膨胀橡胶。通过扫描电子显微镜观察了其微观相态结构 ,适量加入两亲性嵌段共聚物 PEO- b- PBA可以改善 CSP树脂与 NR的相容性。并研究了质量吸水率 ,体积膨胀率以及吸水速率与各组分含量之间的关系 ,对体系的力学性能进行了研究 。

ABA型两亲嵌段共聚物的合成及表征

以α ,α′ 二溴代二甲苯为引发剂 ,CuBr/2 ,2′ 联吡啶为催化体系 ,制备了双溴端基的分子量分布窄的聚苯乙烯 (MWD =1 18) .再以此作为大分子引发剂 ,实现了甲基丙烯酸对硝基苯酯的原子转移自由基聚合 ,制得了分子量可控且分子量分布窄的ABA型嵌段共聚物 ,再经水解、酸化 ,得到了聚甲基丙烯酸 b 聚苯乙烯 b