Wettability of cellular polyurethane

Cellular polymers constitute an important field of investigation due to their unique properties as shock absorbers and thermal or acoustic insulators. The knowledge of the wetting properties of these materials is important in applications where adhesion or weathering behavior are an issue. In this study, cellular polyurethane polymers were used to investigate the effect of the cellular structure on the wetting properties. The polymeric substrates were analyzed by scanning electron microscopy and the wetting properties were studied by goniometry. The contact angles of water and diiodomethane were measured as a function of time and the surface tension of the expanded polymers was evaluated by the geometric and harmonic mean methods. It was found that the wettability and the surface energy of the cellular polymers increase as the density decreases. © 1997 John Wiley & Sons, Inc.     

Synthesis and electro-optical properties of some ferroelectric liquid crystalline polymers

The synthesis and characterization of several series of ferroelectric side-chain polymers were presented. Differential scanning calorimetry, optical polarizing microscopy and X-ray diffraction measurement were used to determine their thermal transitions and analyze their anisotropic textures. The influence of polymer backbones, flexible spacers, mesogenic cores as well as chiral end groups on the mesomorphic properties of the polymers was discussed. Furthermore, the dielectric relaxation properties of the obtained polymers were also evaluated.     

Properties and hydrolysis of PLGA and PLLA cross-linked with electron beam radiation

Radiation has been used as a processing tool to modify the properties of polymers. The aim of this study is to understand how electron beam radiation, together with pentaerythritol tetraacrylate (PTTA) as a tetra-functional monomer, can alter the properties (i.e. thermal and mechanical) and hydrolysis rates of PLGA and PLLA. The effects of radiation dose and PFM concentration on the physical properties of the polymers were investigated. The results showed that upon irradiation PLGA and PLLA cross-linked, and an increased in gel content was observed. Glass transition temperature (T_g) and mechanical properties of the polymers also increased. Cross-linked PLGA and PLLA samples were found to retard hydrolytic degradation. The mechanical properties of these polymers were also unaffected by hydrolysis. In summary, PLGA and PLLA cross-linked with PTTA were found to have enhanced mechanical properties and were able to retard hydrolytic degradation.     

Water soluble nucleic acid analogs: Preparation and properties

In order to prepare water soluble natural and synthetic polymers, which contain nucleic acid base units as the functional side groups, a different sort of polymers, such as poly(ethyleneimine), poly(amino acids) and so on were used as the base materials. The properties of the polymers derived, in particular the specific interaction between nucleic acid base containing complementary polymers was studied in detail. Introduction of the base units onto hyaluronic acid was also carried out. Applicabilities of these polymers obtained, for example as the controlled release system by using reversible photodimerization reaction of thymine bases were also shown.     

Dilational properties of gemini surfactant/polymer systems at the air–water surface

The surface properties of mixed system containing gemini anionic surfactant 1,2,3,4-butanetetracarboxylic sodium, 2,3-didodecyl ester and partly hydrolyzed polyacrylamide were investigated by surface tension measurements and oscillating bubble methods. The influences of surfactant concentration, dilational frequency, temperature, pH, as well as salts on dilational modulus were explored. Meanwhile, the interfacial tension relaxation method was employed to obtain the characteristic time of surface relaxation process. The polymers play important roles in changing the interfacial properties especially at lower surfactant concentration. The possible mechanism of the polymer in changing the interfacial properties is proposed. Both the hydrophobic and electrostatic interaction among the surfactants and polymers dominate the surface properties of mixed system. These dynamic properties are of fundamental interest in understanding the structure of adsorption layers, dynamics of surfactant molecules, and their interaction with polymers at the surface.     

Microscopy and spectroscopy of interactions between metallopolymers and carbon nanotubes

The interaction between redox polymers, based on Ru- or Os-bis(2,2'-bipyridyl)-poly(4-vinylpyridine), and carbon nanotubes was investigated by spectroscopic and microscopic techniques. These metallopolymers were found to be excellent dispersants for nanotubes, as a result of a good wetting interaction between polymer and nanotubes. The results obtained show that well-coated individual nanotubes can be obtained. In addition, interactions between nanotubes and polymers did not significantly affect the electronic and electrochemical properties of the metallopolymers. On the basis of the electrochemical properties of the polymers this opens the possibility of adding functionality through interaction with nanotubes, either as redox active materials with enhanced mechanical properties or by using these modified nanotubes as nanosized electrochemical sensors.     

The influence of different fillers on mechanical and physical properties of high-molecular-weight biodegradable aliphatic polyesters

Poly(ethylene succinate) and poly(butylene succinate) are synthetic biodegradable polymers, and much attention is paid to study the properties of pure polymers and the polymers modified by different comonomers and filling materials. The literature data on the physical properties of these polymers vary widely depending on their method of preparation and subsequent modifications. Most of the studies deal with low- and moderate-molecular-weight polymers or commercial grade polymers, modified by different comonomers and chain-extension agents. The data on pure high-molecular-weight polymers are scarce. In this work, we have prepared high-molecular-weight (MW range of (1.4–1.8) × 10⁵) poly(ethylene succinate) and poly(butylene succinate) by direct polycondensation at 200°C in a nitrogen flow without chain-extension agents. We have further studied the properties of pure polymers and examined the effect of different fillers (carbon nanotubes, SiO₂, Aerosil®) on the mechanical and physical properties of these polymers. Because of high-molecular-weight, the polymers possess increased tensile and storage moduli and thermostability. Even very low filler contents (up to 1 wt %) have a pronounced influence on the polymer properties: the polymer tensile and the storage modulus increases, the elongation at break decreases, and the thermal stability of the polymers decreases slightly. The effects of fillers are less pronounced compared with those for low- and moderate-molecular-weight polymers. When mixed together, poly(ethylene succinate) and poly(butylene succinate) crystallize independently from each other as evident from the mechanical and thermal analysis data.     

Organic-Inorganic Hybrid Materials with the Ability to Bind Metal Ions: Calorimetric Properties and Thermostability

Organic-inorganic hybrid materials with excellent heavy metal ions chelating properties were synthesized by covalent bonding of multifunctional polymers of polyamidoamine (PAA) type onto silica. Two series of polyamidoamine-silica hybrid materials differing in the PAA chemical structure were prepared and their thermal properties were investigated. Differential Scanning Calorimetry was used to study the effects of chain immobilization and ion chelation on the glass-transition temperature (Tg) of the polymers. The Tg of PAA-hybrid materials was elevated with respect to ungrafted PAAs. Complex formation with metal ions such as Cu⁺⁺ or Co⁺⁺ caused total suppression of Tg for both linear polymers as well as the corresponding hybrid materials. Finally, the silica particles slightly influenced the decomposition temperatures of linear polymers increasing their thermal stability.     

Poly(cyclodiborazane)s

This paper summarizes our recent works on the synthesis and properties of the organoboron polymers, especially poly(cyclodiborazane)s. The polymers consist of boron–nitrogen four-membered rings, and are highly stable against air and moisture. The obtained polymers exhibited interesting properties as a novel type of π-conjugated polymers with intramolecular charge transfer structure. Their stability and potential as functional materials would be important and informative both in industry and boron chemistry.     

Through-space conjugated polymers based on cyclophanes

Conjugated polymers display unique electronic and optical properties, which favor their use in applications as optoelectronic materials and molecular devices. Despite the recent remarkable progress in the chemistry of conjugated polymers, the synthesis of conjugated polymers containing cyclophane units in the main chain is limited to only a few examples. This Minireview presents recent developments in the synthesis, properties, and applications of through-space conjugated polymers based on cyclophanes.     

含季铵离子液晶聚合物

详细讨论了带有铵离子的液晶聚合物的合成与性能,以及铵离子对聚合物液晶性能的影响。研究表明,液晶相温度的增加是由铵离子在聚合物链中浓度的增加而引起的。     

Design of molecular imprinted polymers compatible with aqueous environment

The main problem of poor water compatibility of molecularly imprinted polymers (MIPs) was addressed in examples describing design of synthetic receptors with high affinity for drugs of abuse. An extensive potentiometric titration of 10 popular functional monomers and corresponding imprinted and Blank polymers was conducted in order to evaluate the subtleties of functional groups ionisation under aqueous conditions. It was found that polymers prepared using 2-trifluoromethacrylic acid (TFMAA) in combination with toluene as porogen possess superior properties which make them suitable for effective template recognition in water. The potential impact of phase separation during polymerisation on formation of high quality imprints has been discussed. Three drugs of abuse such as cocaine, deoxyephedrine and methadone were used as template models in polymer preparation for the practical validation of obtained results. The polymer testing showed that synthesized molecularly imprinted polymers have high affinity and selectivity for corresponding templates in aqueous environment, with imprinting factors of 2.6 for cocaine and 1.4 for methadone and deoxyephedrine. Corresponding Blank polymers were unable to differentiate between analytes, suggesting that imprinting phenomenon was responsible for the recognition properties.     

Ageing of thermosets based on tung oil/styrene/divinylbenzene

New thermoset polymers prepared by cationic co-polymerization of tung oil with styrene and/or divinylbenzene were evaluated at different times after their preparation. The changes in the properties were correlated with the composition of the copolymers. The action of atmospheric oxygen on the fatty acid unsaturations produced chemical changes in these polymers, which affected the properties of the cured materials. These changes were analyzed by FTIR, dynamic mechanical properties and mechanical testing. An increase in the modulus with time for all the analyzed samples was observed, as well as a large effect on the glass transition temperature and, consequently, in the shape memory properties.     

Amorphous perfluorinated membrane materials: Structure,properties and application

The structure and properties of glassy amorphous perfluorinated polymers are considered with an emphasis of their use as membrane material. The results of the study of free volume in these polymers and simulation of their nanostructure are discussed. The perfluorinated polymers are featured by unusual thermodynamic properties, so the influence of these properties on the parameters of the membranes based on them is examined. In conclusion, various applications of the membranes based on the perfluorinated polymers (predominantly amorphous Teflon AF) in separation processes are described.     

Ion transport in sulfonated polymers

As the focus on proton exchange fuel cells continues to escalate in the era of alternative energy systems, the rational design of sulfonated polymers has emerged as a key technique for enhancing device efficiency. Although the synthesis and characterization of a wide variety of sulfonated polymers have been extensively reported over the last decade, quantitative understanding of the factors governing the ion transport properties of these materials is in its infancy. In this article, we describe the current understanding of the thermodynamics and ion transport in sulfonated polymers. Various strategies for accessing improved transport properties of sulfonated polymers are presented by focusing on their structure-property relationship. The major accomplishment of obtaining well-defined morphologies for these sulfonated polymers is highlighted as a novel means of controlling the transport properties. Recent studies on the thermodynamics, morphologies, and anhydrous transport properties of sulfonated block copolymers comprising ionic liquids, geared towards high temperature polymer electrolyte membranes as a prospective technology, are also expounded. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Conformation Control of Conjugated Polymers

In the past few decades, conjugated polymers have aroused extensive interest in organic electronic applications. The electrical performance of conjugated polymers has a close relationship with their backbone conformation. The conformation of the polymer backbone strongly affects the πelectron delocalization along polymer chains, the energy band gap, interchain interactions, and further affects charge transport properties. To realize a rigid coplanar backbone that usually possesses efficient intrachain charge transport properties and enhanced π–π stackings, such conformation control becomes a useful strategy to achieve high-performance (semi)conducting polymers. This minireview summarizes the most important polymer structures through conformation control at the molecular level, and then divides these rigid coplanar conjugated polymers into three categories: 1) noncovalent interactions locked conjugated polymers; 2) double-bond linked conjugated polymers; 3) ladder conjugated polymers. The effect of the conformation control on physical nature, optoelectronic properties, and their device performance is also discussed, as well as the challenges of chemical synthesis and structural characterization.     

Synthesis,thermal and optical properties of new nanosized polyamides containing N-phenyl- and O-naphthyl-s-triazine rings; part 2

We report the chemistry and properties of two new series of well-defined nano sized spheres aramides-containing N- and O-naphthyl-s-triazines. The polymers were carefully characterized by different techniques including infrared, ultraviolet, fluorescent emission, elemental, thermal analyses and scanning electron microscopy (SEM). The polymers were readily soluble in polar aprotic solvents while insoluble neither in water nor halogenated solvents. Thermal analyses data up to 900°C showed high thermal behavior and the polymers were classified either as “slow burning polymers” or “self-extinguishing polymers” based on their calculated the limiting oxygen index. Interestingly, the naphthyl / phenyl interchange has dramatic improvement on the thermal properties. Obviously, the pyridine / phenylene interchange has no influence on the thermal properties of the addressed polymers. Thermal stability of the aniline-containing polymers proved to be comparable to their naphthylamine analogues. Polymers containing p-phenylene moieties exhibited better thermal results compared to their analogues containing m-phenylene moieties. Benzidine containing polymers and sulfone containing polymers exhibited better thermal stabilities than their analogues containing either ether or methylene flexible linkages. The kinetic data obtained from the nonisothermal decomposition of the prepared polyamides series were also studied. The polymers exhibited emissions ranging from blue to orange wavelength depending on the nature of the signaling unit. The naphthyl / phenyl interchange led to either appreciable red-shifted absorptions in some cases or blue-shifted absorptions in other cases and this behavior may be attributed to the contorted, twisted structural nature of the naphthalene ring. Such attracting properties make these polymers good candidates for applications such as processable high-temperature materials and also as heat-resistant polymeric materials.     

Insulating Polymers as Additives to Bulk-Heterojunction Organic Solar Cells: The Effect of Miscibility

Adding insulating polymers to conjugated polymers is an efficient strategy to tailor their mechanical properties for flexible organic electronics. In this work, we selected two insulating polymers as additives for high-performance photoactive layers and investigated the mechanical and photovoltaic properties in organic solar cells (OSCs). The insulating polymers were found to reduce the electron mobilities in the photoactive layers, and hence the power conversion efficiencies were significantly decreased. More importantly, we found that the insulating polymers exhibited negative effect on the mechanical properties of the photoactive layers, with reduced Young's modulus and low crack onset strains. Further studies revealed that the insulating polymers had poor miscibility with the photoactive layers, providing large domains and more cavities in blend thin films, which act as negative effect for the tensile test. The studies indicate that rational selection of insulating polymers, especially enhancing the non-covalent interaction with the photoactive layers, will be critically important for the stretchable OSCs.     

氮杂环高分子化合物的电催化性能进展

介绍了氮杂环高分子配合物及其电催化性能,归纳了含氮杂环高分子配合物的结构类型及其在界面上的自组装过程,分析了氮杂环高分子自组装膜表面化学反应的特性。对自组装技术制备超薄层材料及表面改性技术在分子电子器件等方面的应用作了评述。     

Novel photoluminescent polymers containing oligothiophene and m-phenylene-1,3,4-oxadiazole moieties: synthesis and spectroscopic and electrochemical studies

Three conjugated polymers containing oligothiophene units (from one to three thiophene rings) and aromatic 1,3,4-oxadiazole moieties have been successfully synthesized. The polymer structures were characterized and confirmed by (1)H and (13)C NMR, FT-IR, and elemental analysis. Thermogravimetric analysis demonstrated that the polymers are highly thermal stable. Tunable absorption (from 342 to 428 nm) and fluorescence (from 411 to 558 nm) properties of polymers were observed. The electrochemical investigation indicated that the LUMO and HOMO energy levels of the new polymers could be adjusted. It was also revealed by the electrochemical analysis that the polymers have good charge injection properties for both p-type and n-type charge carriers, as well as good color tunable luminescence and film-forming properties, which makes them potentially useful for fabricating efficient light-emitting devices.