Synthesis of aramides in solutions of poly(vinylpyrrolidone)

Results on polycondensation of poly(1.4 benzamide) (PBA) and 2.5.DCIPDAcoTPA in solutions of poly(vinylpyrrolidone) (PVP) will be presented. For polycondensation, the method of OGATA, using triphenylphosphine and hexachloroethane, and the low-temperature solution polycondensation of dicarboxylic acid dichlorides and diamines, were applied. It is shown that the molar mass of PBA depends strongly on the PVP:PBA ratio. To explain this dependence, one has to take into account the phase behavior of the ternary rigid rod polymer/flexible coil polymer/solvent system and the influence of the matrix polymer. An enhancement of the molar mass of the PBA produced can be observed when the PVP:PBA is high enough to prevent an association of the PBA, i.e. when one stays in the isotropic one-phase area of the phase diagram. Under these circumstances, it is possible to obtain one-phase systems in nonsolvents for the aramides.     

光学活性三嵌段刚柔共聚物的合成和在二氧六环/水中的自组装

刚柔嵌段聚合物作为多层次有序高级结构的构筑单元正受到广泛的关注．与仅由柔性链段连接而成的嵌段聚合物相比,一方面,刚性链段和柔性链段的相分离与刚性链段倾向于有序取向间的竞争,使其自组装能力增强;另一方面,可在刚性链段引入某些功能基团,从而赋予超分子聚集体识别、传感、催化、光电等特殊的性质．     

Supramolecular nanostructures from self‐assembly of T‐shaped rod building block oligomers

T‐shaped coil–rod–coil oligomers, consisting of a dibenzo[a,c]phenazine unit and phenyl groups linked together with acetylenyl bonds at the 2,7‐position of dibenzo[a,c]phenazine as a rigid segment have been synthesized. The coil segments of these new molecules composed of poly(ethylene oxide) (PEO)–poly(propylene oxide) (PPO) incorporating lateral methyl groups between the rod and coil segment and two flexible alkyl groups connecting with the rigid segment at the 4,6‐position of dibenzo[a,c]phenazine, respectively. The experimental results reveal that the length of the flexible PEO coil chain influence construction of various supra‐nanostructures from lamellar structure to rectangular columnar structure. It is also shown that introduction of different length of alkyl side chain groups in the backbone of the T‐shaped molecules affect the self‐organization behavior to form hexagonal perforate layer or oblique columnar structures. In addition, lateral methyl groups attached to the surface of rod and coil segments, dramatically influence the self‐assembling behavior in the crystalline phase. T‐shaped molecules containing a lateral methyl group at the surface of rod and PEO coil segments, self‐assemble into 3D body‐centered tetragonal structures in the crystalline phase, while molecules without a lateral methyl group based on PEO coil chain self‐organize into 2D oblique columnar crystalline structures. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5021–5028     

Stiffening of Semirigid Polymer Chains Before the Isotropic-Aniostropic Transition

Introduction　　 The conformation of the synthetic polypeptide such as poly(γ-benzyl L-glutamate)(PBLG) or poly(β-phenethyl L-aspartate) (PPLA) is maintained in theα-helix in numerousorganic solvents that supports the intramolecular hydrogen bonding.Above a critical volumefraction of a polymer,the randomness of the orientation along the long axes of the macro-molecule is lost and a lyotropic liquid crystal is formed[1 ] .　　 If the polypeptide is dissolved in a binary solvent mixture c…     

Construction of Supramolecular Assemblies from Self‐Organization of Amphiphilic Molecular Isomers

Amphiphilic coil‐rod‐coil molecules, incorporating flexible and rigid blocks, have a strong affinity to self‐organize into various supramolecular aggregates in bulk and in aqueous solutions. In this paper, we report the self‐assembling behavior of amphiphilic coil‐rod‐coil molecular isomers. These molecules consist of biphenyl and phenyl units connected by ether bonds as the rod segment, and poly(ethylene oxide) (PEO) with a degree of polymerization of 7 and 12 as the flexible chains. Their aggregation behavior was investigated by differential scanning calorimetry, thermal optical polarized microscopy, small‐angle X‐ray scattering spectroscopy, and transmission electron microscopy. The results imply that the molecular structure of the rod building block and the length of the PEO chains dramatically influence the creation of supramolecular aggregates in bulk and in aqueous solutions. In the bulk state, these molecules self‐organize into a hexagonal perforated lamellar and an oblique columnar structure, respectively, depending on the sequence of the rod building block. In aqueous solution, the molecule with a linear rod segment self‐assembles into sheet‐like nanoribbons. In contrast, its isomer, with a rod building block substituted at the meta‐position of the aryl group, self‐organizes into nanofibers. This is achieved through the control of the non‐covalent interactions of the rod building blocks.     

Ordered nanostructures from self‐assembly of H‐shaped coil–rod–coil molecules

A new class of π‐conjugated, skewed H‐shaped oligomers, consisting of biphenyl, phenylene vinylene, and phenylene ethynylene units as the rigid segment, were synthesized via Sonogashira coupling and Wittig reactions. The coil segments of these molecules were composed of poly(ethylene oxide) (PEO) or PEO with lateral methyl groups between the rod and coil segment, respectively. The experimental results revealed that the lateral methyl groups attached to the surface of the rod and coil segments dramatically influenced the self‐assembling behavior of the molecules in the crystalline phase. H‐shaped rod–coil molecules containing a lateral methyl group at the surface of the rod and PEO coil segments self‐assemble into a two‐dimensional columnar or a three‐dimensional body‐centered tetragonal nanostructures in the crystalline phase, whereas molecules lacking a lateral methyl group based on the PEO coil chain self‐organize into lamellar or hexagonal perforated lamellar nanostructures. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 85–92     

Blends of some non-flexible and flexible polymers: Routes to molecular composites?

The definition of a molecular composite is a blend of a rigid rod polymer and a flexible coil polymer that is miscible at the molecular level. This concept has been tested using systems in which the chain flexibilities differ as widely as possible as judged by the difference in glass transition temperatures (δTg). The biggest variation (δT ∼360°C) was obtained by mixing poly benzimidazole with copolymers of poly(vinyl acetate-ran-vinyl alcohol). It was observed that the blends were distinctly two phase when the hydroxyl content was less than 50 mol %. Above this value clear blends were obtained with finely dispersed phases although it is doubtful if mixing at the molecular level takes place. Miscible blends could be obtained from combinations of the sodium salt of poly(phenylene terephthalamide) with poly(4-vinylpyridine) and mixtures of poly(phenyl imino-1,4-phenyleneoxyterephthalate) with poly(styrene-stat-hydroxylstyrene) where coulombic interactions and hydrogen bonding respectively promoted the miscibility.     

缩聚合成聚芳酯和聚酯－聚醚弹性体的微相复合物

通过原位直接缩聚反应，制备了刚性棒状聚对羟基苯甲酸酯（ＰＨＢ）和聚对苯二甲酸丁二醇酯－聚四亚甲基醚多嵌段共聚物（ＰＢＴ－ＰＴＭＧ）的微相复合物．复合物可溶于氯仿等溶剂，可以浇铸成膜．本文研究了ＰＨＢ含量和聚合过程中，基体聚合物溶液浓度对微相复合物形态以及力学性能影响．同共混法相比，原位缩聚法可得到分散更均匀，力学性能更优良的微相复合物．     

分子复合材料的研究与开发动态

由于刚性棒状杂环高分子的出现才导致分子复合材料概念的产生。本文综述了近10年的研究和开发动态,介绍了能作为分子复合材料的增强剂、基体树脂以及研究和开发几种典型的分子复合材料,例如全芳族、聚酰胺热塑性树脂基及耐高温热塑性树脂基分子复合材料的制备和性能,最后预示了复合材料的开发前景。     

缩聚合成聚芳酯和聚酯－聚醚弹性体的微相复合物

通过原位直接缩聚反应，制备了刚性棒状聚对羟基苯甲酸酯和聚对苯二甲酸丁二醇酯－聚四亚甲基醚多嵌段共聚物和微相复合物，复合物可溶于氯仿等溶剂，可以浇铸成膜，本文研究了ＰＨＢ含量和聚合过程中，基体聚合物溶液浓度对微相复合物形态以及力学性能影响，同共混法相比，原位缩聚法可得到分散更均匀，力学性能更优良的微相复合物。     

Conformational and Dynamical Evolution of Block Copolymers in Shear Flow

Conformation and dynamical evolution of block copolymers in shear flow is an important topic in polymer physics that underscores the forming process of various materials. We explored deformation and dynamics of copolymers composed of rigid or flexible blocks in simple shear flow by employing multiparticle collision dynamics integrated with molecular dynamics simulations. We found that compared with the proportion between rigid and flexible blocks, the type of the central blocks plays more important role in the conformational and dynamical evolution of copolymers. That is, if the central block is a coil, the copolymer chain takes end-over-end tumbling motion, while if the central block is a rod, the copolymer chain undergoes U-shape or S-shape deformation at mid shear rate. As the shear strength increases, all copolymers behave similar to flexible polymers at high shear rate. This can be attributed to the fact that shear flow is strong enough to overcome the buckling force of the rigid blocks. These results provide a deeper understanding of the roles played by rod and coil blocks in copolymers for phase interface during forming processing.     

Polycondensation reaction of dimethyl tartrate with hexamethylenediamine in the presence of various matrices

The polycondensation reaction of dimethyl tartrate (DMT) with hexamethylenediamine (HMD) was carried out in dimethyl sulfoxide (DMSO) at 60°C in the presence of various polymer matrices, which were expected to interact with DMT or the resulting polyamide which had pendant hydroxyl groups due to hydrogen bonding. It was found that the rate of polycondensation was enhanced by polymer matrices such as poly(vinyl pyrrolidone) (PVP), Pullulan (polysaccharide) (PF), and poly(vinyl alcohol) (PVA). The rate enhancement became more pronounced with increasing molecular weight of the polymer matrix. When polycondensation in the presence of PVA was carried out in DMSO, a polymer complex was produced. The formation of the polymer complex between the resulting polyamide and PVA during polycondensation was dependent on the concentration of monomers and also on PVA; a gelation of the solution was observed at a concentration of PVA.     

Self-assembly of Amphiphilic Linear Diblock Rod-Coil Molecules by Hydrogen Bond and π-π Stacking Interactions

Aromatic amphiphilic molecules(1) consisting of three biphenyl groups linked together with ether bonds as a rigid rod segment and poly(ethylene oxide) with the number of repeating units of 17 as a coil segment were synthesized, and their self-assembly behavior in the bulk state and aqueous solution was investigated. In bulk, molecules 1 self-assembled into 1-D lamellar structure in the solid state or smectic A phase in the liquid crystalline phase via the cooperative effects of ?-? stacking, micro-phase separation and hydrogen bond interactions. In dilute aqueous solutions, molecules 1 were observed to selfassemble into cylindrical micelles owned uniform diameter and length of hundreds of nanometers.     

Self‐Assembly of Rod–Coil Polyethylenimine–Poly(ethylene glycol)–α‐Cyclodextrin Inclusion Complexes into Hollow Spheres and Rod‐Like Particles

This paper describes the self‐assembly of rod–coil inclusion complexes, polyethylenimine–poly(ethylene glycol)–α‐cyclodextrin (PEI–PEG–α‐CD). It is demonstrated that α‐CDs should exclusively thread on the PEG block in PEI–PEG copolymers and the resulting complexes have both rigid block (PEG–α‐CD) and coil block (protonated PEI). By varying the rigid block fraction, aggregates with hollow spheres or rod‐like particles could be formed simply by self‐assembly in aqueous solution.     

Synthesis of a novel liquid crystal rod–coil star block copolymer consisting of poly(methyl methacrylate) and poly{2,5‐bis[(4‐methoxy‐phenyl)oxycarbonyl] styrene} via atom transfer radical polymerization

A bromine capped star‐shaped poly(methyl methacrylate) (S‐PMMA‐Br) was synthesized with CuBr/sparteine/PT‐Br as a catalyst and initiator to polymerize methyl methacrylate (MMA) according to atom transfer radical polymerization (ATRP). Then, with S‐PMMA‐Br as a macroinitiator, a series of new liquid crystal rod–coil star block copolymers with different molecular weights and low polydispersity were obtained by this method. The block architecture {coil‐conformation of the MMA segment and rigid‐rod conformation of 2,5‐bis[(4‐methoxyphenyl)oxycarbonyl] styrene segment} of the four‐armed rod–coil star block copolymers were characterized by ¹H NMR. The liquid‐crystalline behavior of these copolymers was studied by differential scanning calorimetry and polarized optical microscopy. We found that the liquid‐crystalline behavior depends on the molecular weight of the rigid segment; only the four‐armed rod–coil star block copolymers with each arm's M_n,_GPC of the rigid block beyond 0.91 × 10⁴ g/mol could form liquid‐crystalline phases above the glass‐transition temperature of the rigid block. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 733–741, 2005     

Conditions of formation of liquid crystals from biopolymer solutions

Using the representation of a completely stiff macromolecule as a long rigid rod and the representation of a semiflexible macromolecule as a chain of freely rotating connected effective rigid rods, the conditions of formation of the liquid-crystalline phase in the solutions of such macromolecules are obtained and the diagram of states for the corresponding phase transitions in the variables temperature-volume fraction of polymer in the solution is constructed.     

Gel permeation chromatography with mixed eluents: Polymer solution as mobile phase

The GPC elution behaviour of a polymer was studied when a solution of another polymer in a liquid was used as an eluent. In ternary systems containing two polymers, GPC results are influenced by the thermodynamics of polymer incompatibility. The incompatibility manifests itself both in the slope of the dependence of elution volume upon the concentration of injected polymer and in the shift of elution volumes extrapolated to zero concentration. Experimental data for systems containing poly(styrene) and poly(methyl methacrylate) have been accounted for qualitatively by theoretical views on coil shrinkage resulting from polymer incompatibility. The concentration effects of the injected polymer and the polymer in the mobile phase on elution volume are compared; further parameters affecting the separation in the systems with polymer solution as eluent are discussed.     

Aggregation behavior of poly(γ‐benzyl‐L‐glutamate)‐b‐polyisoprene‐b‐poly(γ‐benzyl‐L‐glutamate) rod‐coil‐rod triblock copolymer in N,N‐dimethylformamide

Solution property of poly(γ‐benzyl‐L ‐glutamate)‐b‐polyisoprene‐b‐poly(γ‐benzyl‐L ‐glutamate) (GIG copolymer) was studied by using dynamic light scattering and static light scattering for N,N‐dimethylformamide (DMF) solution and DMF/toluene mixed solutions. GIG copolymer proved to aggregate in DMF and under DMF‐rich condition, that is, high‐polar region. The aggregate decreased in size, and completely disappeared under toluene‐rich condition, that is, low‐polar region. The correlation between solubility parameter and aggregate size of GIG copolymer in the DMF/toluene solution systems quantitatively demonstrated how strongly polarity caused by hydrogen bond made an impact on the aggregation behavior. Because the main driving force to the aggregation under DMF‐rich condition originates with polyisoprene (PIP) blocks, the aggregate in DMF is considered to be a core‐shell micelle consisting of flexible PIP core surrounded by rigid poly(γ‐benzyl‐L ‐glutamate) (PBLG) shell. The values of dimensionless parameter ρ, defined as the ratio of radius of gyration 〈S²〉^1/2 to hydrodynamic radius R_H, revealed that a single chain of GIG copolymer had the form of rigid rod with flexibility, that is, once‐broken rod, caused by the incorporation of a flexible PIP chain between two rigid PBLG rods in the DMF/toluene solution system. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1740–1748, 2010     

Application of Ultrasonic Attenuation Measurements in the Studies on Macromolecular Conformational Behaviors

——Phase Behavior of the Aqueous Solution of Poly(vinyl methyl ether) Sensitive to Temperature and the Modification of the Behavior by Using Poly(acrylic acid) The phase behavior of the aqueous solution of poly(vinyl methyl ether) (PVME) sensitive to temperature and the modification of the behavior by using poly(acrylic acid) (PAA) have been studied by ultrasonic attenuation measurements and fluorescence probe techniques. It has been observed that PVME solution is transparent at room temperature and becomes turbid upon heating. The solution turns clear again as soon as the temperature is decreased to room temperature. The heating and cooling process can be repeated for many times. The phase behavior of the solution sensitive to temperature is attributed to the conformational changes of the polymer. PVME may adopt an open coil conformation at room temperature. With this conformation, the polymer is well miscible with the solvent, water, and thereby the system is a real solution. The polymer may adopt a compact coil conformation when the temperature is higher than a specific value, which is called the LCST (the lower critical solution temperature) of PVME. In this case, the polymer tangles to each other and forms various aggregates, which can scatter incident light and ultrasonic waves greatly, resulting in the phase separation. Introduction of PAA decreases the temperature sensitivity of the phase behavior of the polymer. The nature of the inhibition is attributed to the complexation of PAA with PVME and the strong hydrophilicity of PAA. Results from fluorescence probe studies are in accordance with those from ultrasonic attenuation measurements, indicating again that the ultrasonic attenuation method can be successfully used for the qualitative studies of polymer conformations and complexation between polymers.     

Molecular composites of polyimide/poly-n-vinylpyrrolidone by in-situ polycondensation

The molecular composites of polyimide (PI) with poly-n-vinylpyrrolidone (PVP) were successfully synthesized by in-situ polycondensation of the rigid polymer in the matrix polymer solution. A strong acid-base interaction between the polyamic acid (the precursor of PI) and the PVP was confirmed experimentally. By this specific interaction the miscibility of PI with PVP was substantially improved. The PI dispersed in the PVP matrix polymer on a molecular level or nearly molecular level.