Synthesis,separation and characterization of knotted ring polymers

Knotted ring polystyrene (PS) with molecular weight of 380 k was successfully synthesized by intramolecular cyclization reaction in cyclohexane under extremely diluted condition. Crude product was confirmed to include linear precursor molecule, single ring molecules, and various intermolecular-reacted byproducts by SEC and interaction chromatography characterizations. The crude product was fractionated repeatedly several times by high performance interaction chromatography and finally highly-purified knotted ring molecules were obtained. It has been found by SEC-MALS that the chain dimension of the knotted ring polymers is evidently smaller than those of linear and the trivial ring polymer, while knotted polymer molecules have the same absolute molecular weight as the corresponding counterparts.     

Self-assembled, optically responsive nematic liquid crystal/polymer core-shell fibers: Formation and characterization

We report here the formation and structural characterization of optically responsive, highly birefringent electrospun nematic liquid crystal (LC) microfibers. The LC microfibers are electrospun from a solution of polylactic acid (PLA) and low molecular weight 4-pentyl-4^’-cyanobiphenyl (5CB) in chloroform/acetone solvent. In the electrospinning process, the low molecular weight 5CB phase-separates and self-assembles to form a planarly aligned nematic core within a PLA shell. The solubility limit of 5CB in PLA and the degree of phase separation of LC in the 5CB/PLA core/sheath fibers is determined using the phase transition enthalpies associated with LC and polymer components. Structural analysis revealed that the LC core and dissolved LC in the fibers promote the formation of the α-form of PLA crystals and increase the degree of crystallinity of the PLA shell in 5CB/PLA fibers from 6.6% to 52%. Competition between 5CB droplet formation and PLA fiber formation is observed as a function of spinning solution composition and applied electrospinning voltage. Alignment of the 5CB within the PLA core is confirmed by polarizing optical microscopy.     

Polymer reaction engineering: From reaction kinetics to polymer reactor control

Polymer reaction engineering is a relatively “young”, very broad, multidisciplinary, rapidly developing field. It is the combination of polymer science, chemistry and technology with process engineering principles. The outcome of this high degree of synergism has evolved over the last fifteen or so years towards an area that includes any or all of the following: polymerization and post-polymerization (chemical modification) reaction kinetics; mathematical modelling and process simulation; polymer reactor design and scale-up; sensor development and process monitoring; and polymer reactor optimization, state estimation and computer control. This article will attempt to give an overview of the results obtained in our laboratory over the last seven years from systematic studies of polymer reaction engineering and polymer production technology problems. These problems cover all aspects of polymer reaction engineering mentioned above. Going from fundamentals to practice, the basic premise of the article is that only by adopting a holistic approach can one devise effective strategies in order to achieve the final objective of more efficient polymer reactor design and control, and hence improved production systems of polymeric materials.     

高分子材料的老化表征方法

高分子材料的老化会使其性能降低,从而部分或完全丧失其使用价值,因此对高分子材料的老化与防老化研究已成为高分子科学的重要研究领域。本文从高分子材料老化过程中外观变化、力学性能变化、电性能变化、波普性能变化4个方面综述了高分子材料的老化表征方法,展望了表征高分子材料老化的研究方向。     

Formation of polymer nanocomposites with various organoclays

The role of the type of organic modifier used with montmorillonite (MMT) on the formation of polymer/clay nanocomposites in the melt compounding process was investigated. Various organoclays including primary [12‐aminolauric acid (12ALA)], secondary [dioctylamine (DOA)], tertiary [trioctylamine (TOA)], and two commercial quaternary (Cloisite 30B and 20A) MMTs were melt compounded with carefully selected polymers including polypropylene, polystyrene, styrene–acrylonitrile copolymer, poly(methyl methacrylate), poly(vinylidene fluoride), and acrylonitrile–butadiene copolymer (NBR). X‐ray diffraction and transmission electron microscopy characterizations confirmed that the two quaternary ammonium organoclay (Cloisite 30B and 20A) have superior compatibility compared to the primary (12ALA), secondary (DOA), and tertiary (TOA) ammonium organoclay. DOA and TOA can form polymer/clay nanocomposites only with the most polar polymer (NBR). Cloisite Na⁺ and 12ALA can not form nanocomposite with any polymers. The large organic surface area of the quaternary ammonium organoclay could be the reason of the best compatibility with polar polymers. It is estimated that long alkyl ammonium chains of organic modifier can spread over the clay surface more effectively than short alkyl chains. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1888–1896, 2005     

支化聚合物的合成及表征

支化聚合物由于其独特的结构和性能以及可实现规模化生产的特点,已迅速成为一类重要的和具有广阔应用潜力的高分子材料。本文综述了近年来制备支化聚合物常用的合成方法：主链引发法、主链-支链偶联法以及单体-大分子单体共聚法;介绍了表征支化聚合物支化度的方法：红外光谱法、核磁共振法、差热分析法、GPC和自动粘度计联用法,并评价了各种方法的优缺点,目的在于加深人们对该领域的了解,从而促进该领域的快速发展。     

氮杂环卡宾-钯功能化的配位聚合物（NHC-Pd@Zn-L）：合成、表征及催化Suzuki-Miyaura交叉偶联反应

以\mathrm{1,3}-二(1-羧乙基)咪唑盐(HL)和Zn(NO₃)₂·6H₂O反应合成二维配位聚合物[Zn(L)₂] _n (Zn-L)，产物再与K₂PdCl₄在四氢呋喃溶液中反应引入氮杂环卡宾-钯（NHC-Pd）催化位点，制得催化剂NHC-Pd@Zn-L，并通过PXRD、TGA、ICP、SEM、EDS和XPS进行表征。结果表明，NHC-Pd@Zn-L具有良好的热稳定性且修饰后晶体的框架结构没有发生变化，Pd以NHC-Pd的形式结合在Zn-L中，并均匀分散在配位聚合物中。将NHC-Pd@Zn-L用于催化Suzuki-Miyaura交叉偶联反应，当以苯硼酸和溴苯为底物，催化剂用量为15 mg，乙醇为溶剂，碳酸钾为碱的条件下60℃反应6 h，产率达到>99%，而且催化剂易于回收并可循环使用3次。     

氮杂环卡宾-钯功能化的配位聚合物（NHC-Pd@Zn-L）：合成、表征及催化Suzuki-Miyaura交叉偶联反应

以\mathrm{1,3}-二(1-羧乙基)咪唑盐(HL)和Zn(NO₃)₂·6H₂O反应合成二维配位聚合物[Zn(L)₂] _n (Zn-L),产物再与K₂PdCl₄在四氢呋喃溶液中反应引入氮杂环卡宾-钯（NHC-Pd）催化位点,制得催化剂NHC-Pd@Zn-L,并通过PXRD、TGA、ICP、SEM、EDS和XPS进行表征。结果表明,NHC-Pd@Zn-L具有良好的热稳定性且修饰后晶体的框架结构没有发生变化,Pd以NHC-Pd的形式结合在Zn-L中,并均匀分散在配位聚合物中。将NHC-Pd@Zn-L用于催化Suzuki-Miyaura交叉偶联反应,当以苯硼酸和溴苯为底物,催化剂用量为15 mg,乙醇为溶剂,碳酸钾为碱的条件下60℃反应6 h,产率达到>99%,而且催化剂易于回收并可循环使用3次。     

Sustainable polymer reaction engineering: Are we there yet?

Polymers are a class of materials that provide unparalleled benefits to humanity, fulfilling countless needs in an exceedingly broad range of applications. Because of their ubiquity and current ways of producing them, polymers also pose significant challenges to the environment. Inspired by a previous publication on sustainable polymer reaction engineering, an update is provided on the latest trends in the use of renewable starting materials for polymers, efforts in process intensification and water‐based polymerization, as well as approaches to dealing with the end of the polymers' application life. We seek to answer the question about how far along we are regarding the achievement of completely sustainable polymer processes.     

高分子梯度玻璃的研制和表征

利用溶胶凝胶法制备高分子梯度玻璃前体 ,在这个体系中加入钛酸丁酯 ,形成高分子梯度玻璃。采用X射线散射能谱 (EDAX)、吸收光谱仪、隧道扫描电子显微镜 (SEM)、射线衍射仪 (XRD)对产品进行了表征 ,发现在样品(棒状 )中钛离子浓度由中心向边缘逐渐降低 ,呈梯度分布 ,样品在可见光范围内无明显的吸收峰 ,说明样品有较好的光学透明性 ,材料的颗粒分布均匀 ,粒径的大小为 40～ 6 0nm ,说明其有机相和无机相是均匀混合的 ,材料中没有明显的晶态物质     

Polyethers with phosphate pendant groups by monomer activated anionic ring opening polymerization: Syntheses,characterization and their lithium-ion conductivities

This paper describes the preparations and lithium-ion conductivities of various solid polymer electrolytes for potential use in high-energy density lithium-ion batteries. The ring opening polymerization of epoxides (M1–M6), catalyzed by Zn(II), Cu(II) and Cd(II) complexes in the presence of tetrabutylammonium bromide (TBAB), yielded polyethers (P1–P6) in which phosphates were attached as pendant groups. A reaction condition where Zn(II) catalyst used slightly excess to TBAB increased the polymerization rate remarkably and yielded the polyethers with higher molar masses in a short time. These polymerizations proceeded following a “monomer activated anionic ring opening polymerization” mechanism. These living like polymerizations also progressed according to “formation of polymer chain per initiator” model. The solid-state lithium-ion conductivities of these polymers were examined using lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The conductivity of one of the solid polymer electrolytes with 40 wt% of LiTFSI was 5.2 × 10⁻⁵ S cm⁻¹ at room temperature and 2.9 × 10⁻⁴ S cm⁻¹ at 80 °C.     

Preparation and characterization of magnetic amphiphilic polymer microspheres

Magnetic amphiphilic polymer microspheres were prepared by copolymerization of styrene with poly(ethylene oxide) macromonomer (MPEO) in the presence of Fe₃O₄ magnetic fluid in ethanol/water medium. Magnetic microsphere size, size distribution, and surface morphology were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The structure of copolymer was determined by infrared spectroscopy. With increasing MPEO used in the polymerization, the resulting microsphere size decreased. Magnetic amphiphilic polymer microspheres containing 0.02–0.2 mmol/g hydroxyl groups could be prepared by using different MPEO concentration. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1847–1851, 2001     

Synthesis and characterization of four-armed star mesogen-jacketed liquid crystal polymer

The synthesis of four-armed star mesogen-jacketed liquid crystal polymer was achieved by atom transfer radical polymerization in chlorobenzene solution using pentaerythritol terakis(2-bromoisobutyrate) (PT-Br) as an initiator and CuBr/sparteine complex as a catalyst. The results show that the number average molecular weigh is creased linearly vs. monomer conversion, and that the polydispersities were quite narrow (<1.19), which is the character of controlled polymerization. The structure was experimentally confirmed by ¹H NMR. The liquid-crystalline behavior of the four-armed star polymer was studied using DSC and POM. Only the polymer with a M_n,GPC beyond 3.68×10⁴ g/mol formed a liquid crystalline phase which was quite stable with a high clearing point.     

苯丙氨酸衍生类多肽聚合物纳米棒的制备及表征

以手性化合物苯丙氨酸作为前驱体,于油酸中通过高温溶剂法一步合成了具有强疏水性的白色类多肽聚合物,扫描电子显微镜分析表明,产物自组装成纳米棒结构。利用核磁共振、紫外光谱、红外光谱、荧光光谱、基质辅助激光解析电离飞行时间质谱等对产物进行了分析。圆二色光谱分析表明,产物仍具有手性性质。该合成方法简单方便,提供了一种合成类多肽聚合物的途径。     

Formation and characterization of perfluorocyclobutyl polymer thin films

Perfluorocyclobutyl (PFCB) polymers are a new class of materials that show promise as selective layer materials in the development of composite membranes for gas separations, such as carbon dioxide/methane (α_{pure gas} = 38.6) and oxygen/nitrogen (α_{pure gas} = 4.8) separations. In many of the flat sheet applications, a thin film of the selective layer that is free of major defects must be coated onto a support membrane. A focus of this study was to elucidate the impacts of solvents, polymer concentration, and dip‐coating withdrawal speed on PFCB thin film thickness and uniformity. An extension was proposed to the Landau–Levich model to estimate the polymer film thickness. The results show that the extended model fits the thickness‐withdrawal speed data well above about 55 mm/min, but, at lower withdrawal speeds, the data deviated from the model. This deviation could be explained by the phenomenon of polymer surface excess. Static surface excesses of polymer solutions were estimated by applying the Gibbs adsorption equation using measured surface tension data. Prepared films were characterized by ellipsometry. Refractive index was found to increase with decreasing film thickness below about 50 nm, indicating densification of ultrathin films prepared from PFCB solutions below the overlap concentration. Atomic force microscopy was used to characterize surface morphologies. Films prepared from tetrahydrofuran and chloroform yielded uniform nanolayers. However, films prepared using acetone as solvent yielded a partial dewetting pattern, which could be explained by a surface depletion layer of pure solvent between the bulk PFCB/acetone solution and the substrate. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and characterization of polynaphthyl amine (PNA) as a novel conducting polymer

A series of polynaphthyl amine (PNA) were prepared in acetone/water mixture (v/v) using different concentrations of potassium persulfate as an initiator in presence and in absence of polyvinyl alcohol (PVA) as a surface active agent. Polymers of various physical properties were prepared. The physical properties of PNA using different concentrations of potassium persulfate in presence and in absence of PVA were given. The specific conductance of the prepared polymers was found to be 0.055 ohm cm, 0.145 ohm⁻¹ cm⁻¹ and 0.083 ohm⁻¹ cm⁻¹, at 3, 1.5, and 0.75% of potassium persulfate, respectively. X‐ray diffraction analysis was carried out to the sample having the highest specific conductance. The confirmation of the prepared PNA was carried out using UV and IR spectrophotometry. Finally PNA showed good air stability and excellent solubility in organic solvents differing from that of polyaniline. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 988–992, 2000     

Structural characterization of semicrystalline polymer blends by small-angle neutron scattering

A series of phase-separated polyethylene-polypropylene blends, which have undergone different thermal treatments, have been analysed by small-angle neutron scattering (SANS). The coherent scattering from normal hydrogenated blends is virtually zero, but strong contrast may be induced by partial or complete deuteration (labelling) of either phase. Here, the scattering from blends with complete labelling of the polyethylene phase was analysed to provide the domain dimensions by means of a theory due to Debye using an exponential correlation function. By this means the mean chord intercept lengths of both phases were shown to be in the range 1000–10000Å. The scattering from blends with partial labelling of the polyethylene was analysed to give the radius of gyration of the molecules in the polyethylene domains, which was found to be close to that measured in the homopolymer. For melt-quenched blends the deuterated polyethylene was shown to be statistically distributed in the polyethylene phase, whereas for slow-cooled blends, partial segregation of the labelled molecules occurred.     

Polysiloxane-poly(fluorinated acrylate) interpenetrating polymer networks: Synthesis and characterization

Combinations of fluorinated and silicone based elastomers were elaborated through the in situ synthesis of interpenetrating polymer networks (IPNs). The PDMS network was formed by dibutyltindilaurate catalyzed addition between the hydroxy end groups of α,ω-(3-hydroxypropyl)polydimethylsiloxane (PDMS) and a pluriisocyanate cross-linker. The poly(fluorinated acrylate) (polyAcRf6) network was obtained from free-radical copolymerization of a fluorinated acrylate with ethylene glycol dimethacrylate in the presence of dicyclohexyl peroxydicarbonate as the initiator. IPNs with different relative weight proportions of the fluorinated vs silicone partners were characterized by DMTA and DSC. Density refractive index and contact angle measurements reveal a satisfactory interpenetration degree of PDMS and polyAcRf6 networks. In addition, these materials present an unusual variation of density values and of the surface properties as a function of the relative weight composition.     

Cationic cyclization of cis-1,4-polybutadiene II. Physico-chemical characterization of the polymer

Information on the structure of cyclized cis-1,4-polybutadiene (CBR) was obtained by means of extensive physico-chemical investigations. Fractionation of typical samples of CBR showed a constant distribution of unsaturations in all fractions. No presence of co-catalyst (aromatic) moiety and conjugated double bonds was found in CBR having a degree of cyclization lower than 40%. Combined IR and ¹³C-NMR analysis allowed to calculate the average length of the polycyclic sequences postulated by the cyclization process. The average length was found to range between three and four cyclohexane rings for a cyclization extent ranging from 15 to 60%. Direct evidence of polycyclic sequences having up to three rings was collected by vapour-phase-chromatograph-mass-spectroscopy (VPC-MS) analysis of the products coming from the pyrolysis of CBR: fragments having higher molecular weight were not detected by our work. Ozonolysis experiments, performed under both reducing and oxidizing conditions, showed only the formation of very large fragments(about 18 butadiene units). The collected data support the cyclization mechanism proposed and account for the technological properties of CBR.     

水溶性导电聚合物的合成与表征

采用溶液聚合法合成了具有水溶性的导电聚合物——聚(N-苯磺酸基苯胺),并用红外光谱、紫外光谱和热重分析等对该聚合物进行了表征。研究表明,聚(N-苯磺酸基苯胺)能完全溶解于水、氨水和盐酸中。盐酸掺杂的聚(N-苯磺酸基苯胺)的电导率为6.0×10-4S cm-1。热重分析表明,聚(N-苯磺酸基苯胺)的热分解过程分为四个阶段。