THE OBSERVATION OF INTERNAL MOTION OF LINEAR POLYSTYRENE CHAINS IN CYCLOHEXANE AROUND θ TEMPERATURE

 A high molecular weight (Mw = 1.85 × 10⁷) polystyrene (PS) with narrow distribution was prepared by high vacuum anionic polymerization in tetrahydrofuran. By use of dynamic light scattering, the dynamics of PS chains in cyclohexane was studied around the θ temperature. For the first time, we have observed the internal motion of polymer chains in solutions below the θ temperature by using dynamic light scattering at smaller angles (even qR_g < 1).     

AN INVESTIGATION ON THE LOW TEMPERATURE RELAXATION OF POLYETHERETHERKETONE

The temperature spectra of internal friction of polyetheretherketone (PEEK) are investigated from 130K to 250K with a multi-function torsion pendulum in the frequency range of 0.1 Hz to 5 Hz. A relaxation process, γrelaxation, appears in the temperature range of the measurement. Its relaxation time distribution in terms of a Gaussian distribution, and the relation between molecular motion mechanism and the distribution characteristic are discussed. The element process of γrelaxation is found to be a disordering one.     

CHEMICAL STRUCTURE DEPENDENCE OF THE INTERNAL ENERGY CONTRIBUTION IN RUBBER ELASTICITY

Conformational elasticity theory recently developed has been used to explore the internal energy contribution tothe elastic force f_e/f as a function of strain for poly(cis-1,4-isoprene) and poly(trans-1, 4-isoprene). Calculated f_e/f values arein good agreement with those obtained experimentally. Results show that behavior of f_e/f is mainly contributed by chemicalstructure, or intramolecular interaction, supporting the experimental observations, and that the internal energy contribution isstrain dependent.     

THE PROPAGATION OF INTERNAL WAVES IN NON-HOMOGENEOUS OCEAN WITH THE BASIC HORIZONTAL CURRENTS

The influence of basic horizontal current on the propagation of internal wave in the non-homogeneous ocean is studied in this paper. By means of pseudo-static hypothesis, the basic equation on propagation of internal wave in the non-homogeneous ocean is derived. By using geometric optics approximation the eikonal equation and transport equation are obtained, at the same time in a sort of fluid field, i. e. M= M(y)i+t-M(x)j, the extended Snell law and analytical solution of the rays are also obtained. The present work is an extension to the ray theory of internal wave in the static ocean.     

高分子线性柔性链在超滤过程中第一类突变现象的观察

利用一种双层结构的膜屏蔽了每个微孔所产生的流场之间的相互作用,从而首次观测到理论上预计的高分子线性柔性链在超滤过程中的第一类突变现象,即仅当宏观流速高于一宏观阈值时,高分子长链方可通过尺寸远小于链无扰半径的微孔,且该宏观阈值与高分子链的长短无关.另外,实验中的过滤膜含有多个微孔,实验结果显示,当一给定的宏观流速低于宏观阈值时,部分微孔会被无法通过的较长的高分子链堵塞,造成未堵塞微孔中的微观流速大于微观阈值.因此,较短的高分子链可从未堵塞的微孔通过滤膜.     

THE ADSORPTION OF LINEAR POLY(N-ISOPROPYLACRYLAMIDE)CHAINS ON SURFACTANT-FREE POLYSTYRENE NANOPARTICLES

The adsorption of linear poly(N-isopropylacrylamide) (PNIPAM) chains on surfactant-freepolystyrene (PS) nanoparticles was used as a model system to study the hydrophobic adsorption of polymeron the surface, because the hydrophobility of PNIPAM can be continuously varied by a small temperaturechange. The adsorption was investigated by a combination of static and dynamic laser light scattering (LLS)measurements, In static LLS, the absolute excess scattered light intensity led to the amount of PNIPAMadsorbed on the surface. In dynamic LLS, the hydrodynamic thickness of the adsorbed PNIPAM layer wasaccurately measured. For a given particle concentration, the adsorption increases as thc PNIPAMconcentration and the incubation temperature increase. The average density of the adsorbed PNIPAM layer isreciprocally proportional to the number of the PNIPAM chains on the surface, revealing a simple scaling ofthe chain density distribution. The adsorption follows the Langmuir's isotherm. The enthalpy changeestimated from the adsorption at 25℃and 30℃is slightly positive, indicating that the adsorption involvesthe coil-to-globule transition of the chains on the surface.     

Brillouin散射研究聚苯乙烯的动态力学性质和弛豫过程

用Brillouin散射研究了聚苯乙烯的动态力学性质和弛豫过程及交联对它们的影响。除了观察到它们的高温(T>T_g)无定形弛豫外,还在交联的聚苯乙烯中发现了一种新的弛豫过程,研究了不同交联结构对这种弛豫过程的影响,求得其活化能为12kcal/mol左右。分析了它们所关联的分子运动机制。     

DYNAMIC LIGHT SCATTERING STUDY ON TRANSLATION DIFFUSION OF 8-ARM STAR POLYSTYRENE IN GOOD AND THETA SOLVENTS

The technique of dynamic light scattering has been used to investigate the translation diffusion behavior of 8-arm star polystyrene (SPS)in a good solvent, tetrahydrofuran (THF) or benzene (BZ) and a theta solvent, cyclohexane (CH), by homodyne photon correlation spectroscopy .The intensityintensity autocorrelation function was analyzed by the method of cumulant. The translation diffusion coefficients have been obtained as a function of temperature and concentration. Under theta condition ,the non-concentration dependence of diffusion coefficient showed the unperturbed Gaussian state o the SPS molecular chain. The different hydrodynamic radii estimated from Stokes- Einstein equation reflected the stretch extent of the arm chain for regular star polymer. The data of diffusion activation energy of SPS in THF, BZ and CH were also obtained respectively.     

非晶聚氯乙烯玻璃化转变过程弛豫时间的温度依赖性研究

通过对非晶聚氯乙烯α内耗峰峰温与测量频率的实验结果的拟合，提出了一种新的玻璃化转变附近弛豫时间的表达式，不仅很好地拟合了实验结果，给出调节参量合理的物理意义，而且为Ｋａｕｚｍａｎｎ疑题（ｐａｒａｄｏｘ）提供了一个合理的解决．     

A SLOW RELAXATION MODE OF POLYMER CHAINS IN A SEMIDILUTE SOLUTION

Dust-free semidilute and concentrated polystyrene(PS)solutions in different solvents were prepared by slow evaporation and in situ anionic polymerization,which removes the effects of troublesome artifacts such as dust contamination and concentration gradient.The dynamics was reexamined by a combination of static and dynamic laser light scattering.In benzene and toluene(good solvents for PS),only one fast diffusive mode of polymer chains can be observed when the concentration(c)is up to 20%,which is attri...     

OPTIMIZATION OF MULTI-STEP LINEAR PROGRAMME TEMPERATURE IN CAPILLARY GAS CHROMATOGRAPHY

An optimal method to select the optimal temperature of multi-step linear programme temperature in capillary gas chromatography, by simultaneously considering the effects of column temperature and differences of column distance to be moved on resolution and analytical times, has been developed. We called this optimal method a moving overlapping resolution mapping method because the immigrating position of solute in column is traced. The validity of this optimal method has been verified.     

检测实验室如何开展质量体系内部审核工作

详细论述了审核的基本概念、开展质量体系内部审核工作的必要性、如何开展质量体系内部审核工作以及中国实验室国家认可委员会的有关政策。     

聚丙烯酰胺凝胶结构非均匀性的动态光散射研究

利用动态光散射技术研究了聚丙烯酰胺 (PAAm)凝胶结构的非均匀性 ,分析了PAAm凝胶结构非均匀性的形成原因及凝胶动态光散射的数据处理方法和分析结果的物理意义 .研究结果表明 ,PAAm凝胶中含有动态相关长度 (LC)不同的两相 ,其中 ,LC 为 10～ 2 0nm的区域是聚合物稀疏相 ,LC 为 85nm左右的区域是聚合物密集相 ,两相的不均匀分布形成了PAAm凝胶结构的非均匀性 .分析表明 ,PAAm凝胶存在两相主要是由于单体和交联剂的溶解度存在差异所致 .随交联度增大 ,PAAm凝胶结构的非均匀性显著增强