Mechanical behavior of a single polymer chain in a non-solvent

Mechanical properties of a single polystyrene chain in mixtures of dioxane and methanol were measured with AFM. The effect of the solubility of the surrounding liquid on mechanical behavior of a polymer chain was examined. In good and Θ solvents, the force-extension curves exhibit a freely jointed chain (FJC)-like trend with good reproducibility. In a non-solvent, the profile of force-extension curve was dependent on the extension speed: an FJC-like nature emerged at the lower speed of 200 nm/s while saw-toothed curves were obtained at the higher speed of 2000 nm/s. The shape of saw-toothed curves varied from measurement to measurement. A force relaxation was also observed in the non-solvent under a fixed extension distance after 2000 nm/s extension. The mechanical behavior in non-solvents suggests that inhomogeneous deformation of a PS chain occurs due to reduction of the chain mobility.     

Multifunctional polymer foams with carbon nanoparticles

Increasingly demanding industry requirements in terms of developing polymer-based components with higher specific properties have recently aroused a great interest around the possibility of combining density reduction through foaming with the addition of small amounts of functional nanosized particles. Particular interest has been given to the creation of lightweight conductive polymers by incorporating conductive carbon-based nanoparticles, related to processing improvements in attaining homogeneous nanoparticle dispersion and distribution throughout the polymer as well as new processes that enable a higher control and throughput of highly pure carbon nanoparticles, which could overcome some of the common problems of conductive polymers, such as high cost and poor mechanical properties. This review article considers the use of carbon nanoparticles in polymer foams, initially focusing on the important aspects of foam preparation, the main results found in the literature about conductive polymer composites containing carbon nanoparticles, as well as the main polymer foaming processes and types of foams. The main section is dedicated to the properties of multifunctional polymer foams with carbon nanoparticles, with special focus being given to the electrical and transport properties of these materials.     

Silicon-containing polymer nanosheets for oxygen plasma resist application

In this paper, we prepared a silicon-containing polymer nanosheet, poly(neo-pentylmethacrylamide-co-4-(trimethylsilyl)phenyl)methacrylamide (p(nPMA/SiPhMA)), for positive-tone photoresist application. p(nPMA/SiPhMA) forms a stable monolayer at the air-water interface and the polymer monolayer can be transferred onto a solid substrate using the Langmuir-Blodgett technique, when the SiPhMA molar contents are below 38%. Sixty layers of p(nPMA/SiPhMA) nanosheet were deposited onto a silicon substrate and deep UV was irradiated through a photomask to the deposited film. After development of the irradiated film with alkaline solution, a positive-tone fine pattern with a 0.75 μm resolution, which is the highest resolution of the photomask, was clearly drawn. UV-vis and FT-IR spectroscopy indicates the formation of alkaline soluble groups, such as CO and Si-O-Si after photodecomposition. Moreover, p(nPMA/PhSiMA) polymer nanosheet shows three times higher oxygen etching resistance compared to poly(methylmethacrylate) (PMMA). The high plasma resistance of the polymer nanosheet film is caused by not only the presence of Si atom in the film but also a closely packed and high molecular orientated structure of the polymer nanosheets.     

Mixing of a self-assembled supramolecular polymer and a covalent polymer in organic solutions

We report on a neutron scattering study of the molecular structure of a self-assembled supramolecular polymer composed of a bicopper complex within a solution of a covalent polymer (atactic polystyrene/trans-decalin). The study is achieved by putting two binary phases in contact and allowing for diffusion of both components in either phase. It is shown that the one-dimensional bicopper filaments are compatible to a high extent with the atactic polymer. These results are discussed in the light of a recently devised encapsulation process of the bicopper filaments within the fibrils of a physical network of isotactic polystyrene.     

Influence of molecular weight of polymer matrix on the structure and rheological properties of graphene oxide/polydimethylsiloxane composites

The structure and rheological properties of graphene oxide (GO)/polydimethylsiloxane (PDMS) composites are examined as the molecular weight of PDMS and concentration of GO are varied. Clusters formed by GO sheets get smaller and disperse better with increasing molecular weight of PDMS, which results in the higher critical concentration to form network (C_cr). Moreover, at GO concentration just above C_cr, the plateau modulus of samples decreases with the molecular weight of PDMS. During shear experiments, negative normal stress differences (ΔN) are observed in composites with PDMS molecular weight lower than critical entanglement molecular weight (M_c). However, positive ΔN is found in samples with PDMS molecular weight above M_c. It can be concluded that the vorticity alignment of GO clusters induces the negative ΔN based on the optical shear experiments. The possible mechanism for the positive ΔN is also proposed.     

Mechanical deformation of a liquid crystal diffraction grating in an elastic polymer

We demonstrate the tuning of the diffraction efficiency in a polymer-dispersed liquid crystal (PDLC) diffraction grating by mechanical shear deformation. We chose a photocurable thermoset with elastic mechanical properties as the host material to demonstrate the tuning effect. Raman–Nath gratings were prepared by anisotropically curing a mixture of commercial photopolymer doped with liquid crystal. The mixture was contained between glass slides which were mounted in a simple shearing device. During the photopolymerization, the liquid crystal phase separated into 2-μm droplets organized into channels with 3.8-μm spacing. Gratings were deformed by shearing the samples in a direction perpendicular to the channel orientation. The diffraction intensity and morphology were monitored as a function of shear strain. Reversible tuning was observed due to the elastic nature of the matrix. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 523–526, 1998     

Mechanical properties of blocked polyurethane/epoxy interpenetrating polymer networks

The mechanical properties of blocked polyurethane(PU)/epoxy interpenetrating polymer networks (IPNs) were studied by means of their static and damping properties. The studies of static mechanical properties of IPNs are based on tensile properties, flexural properties, hardness, and impact method. Results show that the tensile strength, flexural strength, tensile modulus, flexural modulus, and hardness of IPNs decreased with increase in blocked PU content. The impact strength of IPNs increased with increase in blocked PU content. It shows that the tensile strength, flexural strength, tensile modulus, and flexural modulus of IPNs increased with filler (CaCO₃) content to a maximum value at 5, 10, 20, and 25 phr, respectively, and then decreased. The higher the filler content, the greater the hardness of IPNs and the lower the notched Izod impact strength of IPNs. The glass transition temperatures (T_g) of IPNs were shifted inwardly compared with those of blocked PU and epoxy, which indicated that the blocked PU/epoxy IPNs showed excellent compatibility. Meanwhile, the T_g was shifted to a higher temperature with increasing filler (CaCO₃) content. The dynamic storage modulus (E′) of IPNs increased with increase in epoxy and filler content. The higher the blocked PU content, the greater the swelling ratio of IPNs and the lower the density of IPNs. The higher the filler (CaCO₃) content, the greater the density of IPNs, and the lower the swelling ratio of IPNs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1826–1832, 2006     

Synthesis of flake-like graphene from nickel-coated polyacrylonitrile polymer

Graphene can be synthesized from polyacrylonitrile (PAN) polymer through pyrolysis. A metal catalyst such as nickel (Ni) is required for the conversion of the polymer to graphene. The metal catalysts can be placed either atop or underneath the polymer precursor. We observed that spatially non-uniform and disconnected graphene was fabricated when PAN film coated with a Ni layer was pyrolyzed, resulting in flake-like graphene. Formation of the flake-like graphene is attributed to the dewetting of the Ni layer coated on the PAN film. Dewetting phenomenon can be reduced by decreasing the pyrolysis temperature, and hence, more uniform graphene could be prepared. The effects of Ni coating thickness and the pyrolysis temperature on the fabricated graphene have been experimentally analyzed.     

A facile approach to the fabrication of ultrathin polymer films and application to optical lenses

A facile approach to the fabrication of ultrathin polymer films on a flat or curved substrate is presented. Polymers with unsaturated pendant groups were spin-coated on a photoinitiator tethered surface, which was then photoirradiated and washed with a solvent. The obtained films were uniform, smooth (R_a < 0.2 nm) and exhibited robustness toward solvents. The thickness of the films was determined by the molecular weight of the coated polymer and was not dependent on the initial spin-coated thickness. A mechanism for the formation of the ultrathin film and application to optical lenses is presented.     

Graphene-based polymer nanocomposites

Graphene-based materials are single- or few-layer platelets that can be produced in bulk quantities by chemical methods. Herein, we present a survey of the literature on polymer nanocomposites with graphene-based fillers including recent work using graphite nanoplatelet fillers. A variety of routes used to produce graphene-based materials are reviewed, along with methods for dispersing these materials in various polymer matrices. We also review the rheological, electrical, mechanical, thermal, and barrier properties of these composites, and how each of these composite properties is dependent upon the intrinsic properties of graphene-based materials and their state of dispersion in the matrix. An overview of potential applications for these composites and current challenges in the field are provided for perspective and to potentially guide future progress on the development of these promising materials.     

A nucleation mechanism leading to stacking of lamellar crystals in polymer thin films

Systematic studies based on well‐controllable model systems aim at understanding how crystallization from a melt or solution of randomly coiled polymers leads to the formation of mono‐lamellar crystals. However, besides mono‐lamellar crystals also various other morphologically simple but yet not well understood structures are found. In particular, stacks of correlated lamellar crystals have been observed since the early days of the study of polymer crystallization. Here, we demonstrate that a recently proposed mechanism of self‐induced nucleation within lamellar crystals provides a possibility to explain how in such stacks lamellar crystals can be correlated. Examining various polymer systems, we show that the probability for generating self‐induced nuclei depends on the morphology of an initiating dendritic basal lamellar crystal. In addition, we provide evidence that this self‐induced nucleation mechanism, together with a high rate of transport of molten polymer to the fold surface, may allow the formation of polymer crystals with similar size in all three dimensions, containing a large number of superposed correlated lamellae. © 2019 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

LiTFSI-乙酰胺熔盐与聚丙烯膜复合的聚合物电解质的研究

二(三氟甲基磺酸酰)亚胺锂LiN(SO2CF3)2,即LiTFSI与乙酰胺形成的新型室温熔盐具有优良的电化学性质和热稳定性。以高强度的聚丙烯多孔薄膜为基体,制备了这种与熔盐体系复合的新型聚合物电解质,测试表明其具有良好热稳定性、电导率高等特点,室温电导率为0.27×10-3S/cm,60℃电导率为1.46×10-3S/cm。     

Electrical properties of a cyclotriphosphazene matrix polymer: Cyclotri(trifluoroethoxy, acryloyloxy-ethyleneoxy)phosphazene matrix polymer

Cyclotri(trifluoroethoxy, acryloyloxy-ethyleneoxy)phosphazene compound is synthesized from the cyclic trimer of dichlorophosphazene by replacing two CI atoms with trifluoroethoxy and acryloyloxy-ethyleneoxy groups. This compound was polymerized by UV irradiation with the aid of a photosensitizer. The polymerization proceeds in the acrylate group by opening the double bond. Whereas the matrix polymer is an insulator at low temperatures, it is a semiconductor at high temperatures. Namely, the conductivity is 8.84×10^–9 S/cm at 19.2°C and 1.17×10^–6 S/cm at 75.0°C. Both dielectric constant and dielectric loss increase with increasing temperature and with decreasing frequency. The conductivity of the cyclotri(trifluoroethoxy, acryloyloxy-ethyleneoxy) phosphazene monomer is higher than that of the corresponding polymer and the dielectric constants are higher at lower frequencies. These results are consistent with the existence of a charge transfer complex.     

Influence of polymer polarity on photochromic behavior of naphthodipyran doped in different polymeric matrixes

Photochromic polymer films were prepared by doping the naphthodipyran into different polymers such as Polyvinylpyrrolidone (PVP), styrene‐butadiene‐styrene (SBS) triblock copolymer, and polymethyl methacrylate (PMMA) at different concentrations. The kinetics of the photochromism/decoloration in the thin films was quantified by fitting biexponential equations to their photochromic decay curves after UV irradiation. The results show that the fastest decoloration process was in SBS, and the slowest one was in PVP. The DSC results indicate that T_g of polymeric matrix has no obvious effect on the decoloration rate of naphthodipyran. The decreasing order of the decoloration constant of naphthodipyran was consistent with increasing polarity of polymer matrixes as PVP > PMMA > SBS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

一种接枝型高分子表面活性剂的合成

以羧甲基纤维素钠为主链,将氯化十二烷基二甲基烯丙基铵(JT-12)接枝串联到高分子链上,形成接枝型高分子表面活性剂,并对其合成条件及表面活性进行研究。结果表明,在弱碱性条件下,40℃~60℃内,羧甲基纤维素钠与JT-12质量比5∶1,反应5 h左右,引发剂加量3.16×10-3mol/L时,产物的接枝率较高,表面活性也较高。     

Bipolar plate materials for solid polymer fuel cells

The interfacial ohmic losses between the bipolar plate and the MEA can significantly reduce the overall power output from a SPFC. For graphitic bipolar plate materials, these losses are insignificant relative to stainless steel, where the existence of a passive film on the surface greatly reduces electrical conductivity. In this paper we have evaluated different bipolar plate materials, and present long-term fuel cell data for Poco^® graphite, titanium, 316 and 310 stainless steel. The properties of the passive film on the surface of 316 and 310 stainless steel are markedly different. Although both were adequately corrosion resistant in a fuel cell environment, 310 tended to produce higher fuel cell performance and like 316, no degradation was observed after 1400 h testing. Analysis of the passive film indicated that this increased performance was related to the decreased thickness of the oxide film.     

PVC装置降膜吸收塔低聚合物垢的化学清洗

论述了PVC合成装置降膜吸收塔低聚合物垢产生的原因、机理、组成及其化学清洗方法.     

Observation of polymer film drawing by use of thermography. An introductory investigation on the thermodynamics

The local heat generation that accompanied tensile drawing of polymer films was successfully observed by infrared thermography as a series of temperature distribution images. These images showed that the high temperature part where rearrangements of molecular orientation and microcrystallines occurred was located mainly at the end of the necked part for the polymers that exhibited necking or appeared uniformly throughout films for the polymers that did not exhibit necking. The generated heat could be roughly estimated, and the relation between the estimated heat and mechanical work led to the thermodynamic investigation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2895–2900, 2006