Dynamic Light Scattering Studies on Crystallization of Isotactic Polystyrene from Dilute Solutions at High Supercoolings

Crystallization of isotactic polystyrene (it‐PS) from dilute solution at high supercooling has been investigated by dynamic light scattering (DLS). We successfully obtained simultaneously, in situ in solutions, the time developments of both random coils of it‐PS molecules and the growing crystals. The size of coils remains constant during growth, while the crystals pass through two stages, that is, an induction period at the early stage with very slow growth rates and a subsequent linear growth stage. It is confirmed that the temperature dependence of the linear growth rates, determined by DLS, agree well with that determined by electron microscopy. The temperature dependences of the growth rate and the inverse of induction time are dependent on the viscosity of solvent, which indicates that all dynamics are dominated by the segmental motion of polymer chains in solution at high supercoolings (low temperatures). Two possibilities are proposed for the induction period.     

Simultaneous measurement of transient stress and flow birefringence in one-sided compression (biaxial extension) of a polymer melt

Summary Investigation of time dependent behaviour of a polystyrene melt is carried out with the aid of a new apparatus for biaxial extension. Use is made of the method of two impinging fluid streams guided by lubricated trumpet shaped metal walls. The flow birefringence is measured in the plane of symmetry and, at the same time, the force is measured which tends to separate the trumpets. The linear stress-optical relation turns out to be valid in this new flow geometry. An accurate value for the stress-optical coefficient can be determined from the relaxation experiments. The stress build-up as calculated from the optical measurements, is compared with the pertinent result of the theory of linear viscoelasticity. For the desired interconversion of dynamic moduli use is made of the approximation by Schwarzl and Struik. The steady state measurements are checked by the results of the non-linear model of Acierno et al.With 16 figures and 2 tables     

Linear elastico-viscous properties of molten standard polystyrenes

This paper contains an extensive presentation of dynamic mechanical data (complex moduli), as obtained on the melts of a series of standard polystyrenes of narrow molar mass distributions. It also shows the way of obtaining structural parameters (plateau modulus and friction factor) which are needed for an interpretation of these data in terms of simple theoretical models (Maxwell elements, Doi-Edwards model). A linear mixing rule is used for taking into account the finite width of the molar mass distributions.Dedicated to Prof. F. R. Schwarzl on the occasion of his 60th birthday     

Improving self-assembly quality of colloidal crystal guided by statistical design of experiments

A versatile and reliable approach is created to fabricate wafer-scale colloidal crystal that consists of a monolayer of hexagonally close-packed polystyrene(PS) spheres. Making wafer-scale colloidal crystal is usually challenging, and it lacks a general theoretical guidance for experimental approaches. To obtain the optimal conditions for self-assembly, a systematic statistical design and analysis method is utilized here, which applies the pick-the-winner rule. This new method combines spin-coating and thermal treatment, and introduces a mixture of glycol and ethanol as a dispersion system to assist self-assembly. By controlling the parameters of self-assembly, we improve the quality of colloidal crystal and reduce the effect of noise on the experiment. To our best knowledge, we are first to pave this path to harvest colloidal crystals.Importantly, a theoretical analysis using an energy landscape base on our process is also developed to provide insights into the PS spheres' self-assembly.     

Fluorescence and absorption of polystyrene exposed to UV laser radiation

We show that when polystyrene is exposed (for 15–60 sec) to a UV laser light beam (λ = 248 nm), its absorption and luminescent properties change significantly. In the irradiated polymer, optical centers are formed with absorption bands in the 280–460 nm region and fluorescence bands in the 330–520 nm region. We have established the chemical structure of the optical centers for fluorescence of polystyrene. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 54–58, January–February, 2006.     

Small angle x—ray scattering study on the conformation of polystyrene in toluene during adding anti—solvent CO2

The conformatiopn of polystyrene in the anti-solvent process of supercritical fluids(compressed CO2 polystyrene toluene)has been studied by small angle x-ray scattering with synchrotron radiation as an x-ray source.Coilto-globule transformation of the polystyrene chain was observed with the increase of the anti-solvent CO2 pressure;i.e.polystrene coiled at a prssure lower than the cloud point pressure(Pc)and turned into a globle with a uniform density at pressures higher than Pc.Fractal behaviour was also found in the chain contraction.and the mass fractal dimension increased with increasing CO2 pressure.     

JSOG中水蒸汽含量的模拟计算

氧碘化学激光（简称 COIL）系统中，水是影响激光功率输出的最重要的原因之一。气流中的水不仅对激发态碘原子有严重的猝灭作用，另外对碘分子解离、超音速流动特性也有很坏的负面作用。单重态氧发生器的BHP（Basic Hydrogen Peroxide ）溶液是最主要的水蒸汽源。利用传质模型对射流式单重态氧发生器（简称JSOG）中产生的水蒸汽进行了计算，所得的数值结果与实验测量结果基本相符。根据模拟结果，对发生器的设计及实验条件进行了优化。     

真空中聚苯乙烯交联材料的沿面闪络特性

搭建了真空沿面闪络实验平台,在实验平台上对聚苯乙烯交联材料进行了真空沿面闪络性能测试,探讨了材料的真空沿面闪络电压强度与材料结构、材料内部微量杂质的关系。实验结果表明:随着聚苯乙烯材料交联程度的增加,其真空沿面闪络电压强度先增加后减少;聚苯乙烯交联材料分子链结构对其真空沿面闪络电压强度有重要影响;材料的真空沿面闪络电压强度还与交联材料内部异质分子数量有关系,微量异质结构的分子将导致沿面闪络电压强度的下降。     

ICF氘代固体靶的研制

 以自制全氘代苯乙烯单体(氘代率99%)为原料, 以偶氮二异丁腈为引发剂, 经自由基本体聚合反应, 先制得全氘代聚苯乙烯, 最后采用乳液微封装技术制得了直径150～450μm、壁厚2～15μm、球形度≥99.5%、同心度95%～98%、表面粗糙度＜30nm的ICF固体靶用空心微球。介绍了制备工艺,并对全氘代聚笨乙烯分子量及其分布的控制,微球壁内气泡形成机理,微球储存稳定性等进行了初步探讨。