THERMAL BEHAVIOR OF THERMOTROPIC HYDROXYETHYL CELLULOSE ACETATE/POLYETHYLENE BLENDS

The thermal behavior of thermotropic hydroxythyl cellulose acetate (HECA)/polyethy-lene (PE) blends has been studied by DSC. It is found that the blends of HECA and PEare immiscible but the crystallization of PE is affected by HECA chains in the blends withmore than 50% HECA, which results in the subordinate crystallization of PE and the for-mation of imperfect structures in the PE crystals. The imperfection of PE crystals in theblends can be eliminated after annealing at 393K.     

胆甾液晶／聚合物多组分体系的结构与性质研究──I．胆甾醇壬酸酯／聚（甲基丙烯酸甲酯－甲基丙烯酸丁酯）混合体系的相变行为

应用ＤＳＣ、偏光显微镜和动态力学分析，研究了胆甾液晶与甲基丙烯酸甲酯－甲基丙烯酸丁酯无规共聚物共混体系的相容性及相态转变．表明共聚物的组成、分子量大小可抑制胆甾液晶的相态转变．给出了形成稳定相容的液晶／高分子体系的最佳条件．     

聚对偶氮氧苯酚酯系列热致性液晶高分子的相转变

合成含有不同亚甲基数（ｎ＝４—１２，１４）的主链型热致性液晶高分子──聚对偶氮氧苯酚二元羧酸酯．用ＤＳＣ和ＦＴＩＲ观测了相转变的奇偶效应，揭示了液晶相转变过程中分子间相互作用力性质的变化．并与聚２，２＇－二甲基对偶氮氧苯酚二元羧酸酯系列进行了比较，讨论了中介单元的对称性对液晶高聚物相转变和对液晶相稳定性的影响．     

STUDY ON THE PHASE TRANSITION KINETICS OF THERMOTROPIC LIQUID CRYSTALLINE AROMATIC-ALIPHATIC COPOLYESTER

The phase transition kinetics of thennotropic liquid crystalline aromatic-aliphatic regular copolyester: were studied by DSC. By means of Kissinger's method the kinetic equation and parameters including activation energy, rate order and preexponential factor for phase transition from nematic to isotropic were obtained. The activation energy from crystal to nematic was also presented.     

序列嵌段共聚酯液晶高分子相转变动力学及机理研究

用DSC、PLM、WAXD等方法研究了序列嵌段共聚酯液晶高分子的结晶动力学及相转变机理.结果表明,从各向同性相温度(T_i)结晶经历了中介相阶段,从中介相温度(T_N)和从T_i温度结晶的结晶机理均为取向链段的聚集成核及低维生长,Avrami指数都接近2.两种结晶途径均形成了不同完善程度的结晶形态.柔性嵌段PTHF含量对试样的液晶行为和结晶行为有很大影响,PTHF含量在20％左右向列型中介相表现出高取向,易成核的特性.     

STUDIES ON THE KINETICS OF PHASE TRANSITIONS OF A MAIN CHAIN THERMOTROPIC POLYESTER

The kinetics of phase transitions including a transition between mesophases were studied for a main-chain thermotropic polyester by means of DSC and depolarizing transmittance techniques. The isothermal process of these transitions was found to be described by the Avrami equation to high conversions. The Avrami exponents n are about 2,4, 5.3 and 2.2 for liquid crystallization, transition between mesophases and crystallization from mesophase respectively. The liquid crystallization from isotropic liquid phase occurs at very low undercoolings with high transformation rate. This behavior is explained as the results of the smaller value of the surface free energy for mesophase than that for crystallites which is evidenced by the very weak temperature dependence of liquid crystallization rate.     

木质纤维素纳米纤丝制备及形态特征分析

以阔叶树材杨木木粉为原料,始终保持纤维处在水润涨的状态下,利用亚氯酸钠在酸性条件下脱除木质素,氢氧化钾脱除半纤维素,然后借助高强度超声波的空化作用,依次制备了综纤维素、纯化纤维素及木质纤维素纳米纤丝(WCNF).通过傅里叶变换红外吸收光谱(FTIR)、X射线衍射(XRD)、扫描电镜(SEM)对WCNF制备过程中的化学组分、晶型结构、结晶度及形态特征变化进行了表征,并进一步利用图像分析系统对WCNF的直径分布进行了测量统计.结果表明,WCNF的主要成分为纤维素,其晶型结构仍为纤维素Ⅰ型,结晶度为65.68%,较之原料木粉提高了12.33%.所得纤丝的直径集中分布在5～32nm之间,长度大于10μm,长径比高于300,纤丝间相互交织成网状缠结结构.WCNF的高结晶度、高长径比、纳米尺度、网状缠结结构,显示其为一种十分理想的增强增韧材料.     

一个新的液晶相转变动力学理论

本文以保留系统的宏观特性为基本原则,从用动力学方法处理非稳态相转变入手,在物理化学基础上,建立了描述液晶相转变的动力学方程,提出了动力学意义上的相转变级数参数,推导出相转变级数的理论公式及参数的变化范围,丹卉将其应用于一新的聚合物体系,获得了该体系各聚合物加热过程中所经历相态的动力学相转变级数。     

N-异丙基丙烯酰胺温度敏感性水凝胶相转变动力学研究及其应用

研究指出表观二级动力学方程可以很好地描述N-异丙基丙烯酰胺水凝胶的溶胀和消溶胀动力学.即溶胀动力学方程为dR/dt=k_1(R_e-R)~2,消溶胀动力学方程为-dR/dt=k_c(R-R_e)~2.把这种水凝胶用于分离高分子水溶液时可引入“单位溶张比分离循环的合理时耗”这样一个参量.它根据溶胀和消溶胀过程中的起始溶胀比、平衡溶胀比、表观溶胀动力学常数和表观消溶胀动力学常数求出.具体公式为△t_1(T_s,T_c)=2/[R_c(T_s)-R_0(T_s)]~2k_s(T_s)+15/[R_0(T_c)- R_s(T_c)]~2k_c(T_c)~(1/2)在理想情况下,分离过程的“总合理时耗”与△t_1成正比,比例系数为分离过程中的除水总量与干凝胶用量的比值,即△t_r=W_W/W_G·△t_1.当根据二个动力学方程求得的总时耗计算值处于(0.9△t_r,1.1△t_r)范围内时,表明所选干凝胶用量和循环溶胀比区段均合适.     

SMALL ANGLE LIGHT SCATTERING MEASUREMENT OF THE ISOTROPIC TO NEMATIC TRANSITION OF A SIDE CHAIN NEMATIC POLYMETHACRYLATE*

The kinetics of I→N transition of a side chain nematic polymethacrylate has been studied by small angledepolarized light scattering intensity measurements using a charge coupled device linear image sensor. The polymer showsthe transition temperatures K52N79I in ℃. The H_v scattering intensity J(q,t) during the transition I (at 80.2℃)→N (at75.8℃) shows that J(q) is independent of q for all t, and during the initial stage (in 6 s) J(t) increases exponentially with t.In the later stage of the transition J(t) approaches a saturation value in 2 min. This experimental result indicates that the I→Ntransition of a liquid crystalline polymer is a spinodal type of phase transition mediated by orientation fluctuation.     

STRUCTURAL PHASE TRANSITION OF ALIPHATIC NYLONS VIEWED FROM THE WAXD/SAXS AND VIBRATIONAL SPECTRAL MEASUREMENTS AND MOLECULAR DYNAMICS CALCULATION

The crystalline phase transition of aliphatic nylon 10/10 has been investigated on the basis of the simultaneous measurement of wide-angle and small-angle X-ray scatterings, the infrared spectral measurement and the molecular dynamics calculation. An interpretation of infrared spectra taken for a series of nylon samples and the corresponding model compounds was successfully made, allowing us to assign the infrared bands of the planar-zigzag methylene segments reasonably. As a result the methylene segmental parts of molecular chains were found to experience an order-to-disorder transition in the Brill transition region, where the intermolecular hydrogen bonds are kept alive although the bond strength becomes weaker at higher temperature. The small-angle X-ray scattering data revealed a slight change in lamellar stacking mode in the transition region. The crystal structure has been found to change more remarkably in the temperature region immediately below the melting point, where the conformationally disordered chains experienced drastic rotational and translational motions without any constraints by hydrogen bonds, and the lamellar thickness increased largely along the chain axis. These experimental results were reasonably reproduced by the molecular dynamics calculation performed at the various temperatures.