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.

聚己内酯和聚氧化乙烯共混体系中的两类片晶相间堆砌

对聚(ε-己内酯)(PCL)/聚氧化乙烯(PEO)共混物的相差显微镜、广角X-射线衍射(WAXD)、小角X-射线散射(SAXS)及示差扫描量热计(DSC)等的研究表明,只有当共混物中PCL(或PEO)的含量低于20％时,两组份是相容的.当PCL含量低于20％时,在共混物中形成了PEO片晶和PCL片晶相间堆砌的结晶形态,当PEO含量不超过20％时,PEO则完全以非晶形式混入PCL的非晶区,同时阻碍了PCL的结晶.可见在结晶过程中,相容的两组份对共混体系形态结构的影响却不尽相同.

聚环氧乙烷(PE0)与聚双酚A羟基醚(PBHE)共混体系的研究

用偏光显微镜(PLM)、扭辫(TBA)、IR及WAXD对PEO/PBHE共混体系结晶形态进行了研究。结果表明,PEO含量在50％以上的共混体系,几乎完全被PEO球晶充满,非晶态PBHE作为微区分散在大球晶之间或球晶之中。PEO含量为40％和30％的照片上呈现树枝晶。PEO含量为20％以下时照片中不再看到结晶出现,PEO与PBHE形成单一非晶相。PEO/PBHE共混体系的组分之间存在着氢键相互作用,这种作用强于PBHE分子间的氢键作用。共混体系的结晶度及T_g随PBHE组分含量的增加,前者减小后者增加并符合FOX方程揭示的规律。PEO与PBHE具有很好的相容性。

乙烯-α-烯烃共聚物的结晶性能及其临界序列结晶长度的研究

本文用DSC、WAXD及偏光显微镜(PLM)方法,研究了化学反应法催化剂合成的乙烯-α-烯烃共聚物的结晶性能及其临界序列结晶长度。结果表明,随共聚物中α-烯烃含量增大,共聚物的微晶尺寸、结晶度及熔点均逐渐减小,而晶胞参数增大。变化的辐度戊烯>辛烯。共聚物的临界结晶序列长度(n)和k值均戊烯<辛烯。上述结果表明影响支链进入晶格的主要因素是α-烯烃支链长度和结构。

化学法镁钛系高效载体催化剂多活性中心的DSC证据

用高效载体钛催化剂进行乙丙共聚物的合成,已有大量报道,但从聚合产物热分析出发对其催化活性中心的性质进行探讨,报道尚少。我们用化学反应法制备的高效载体钛催化剂进行乙丙共聚反应,所得产物进行热分析结果表明,共聚产物具有很宽的链段序列分布,呈现出吸热双峰模式,与催化体系及其聚合过程ESR分析,共聚物溶剂萃取及其~(13)C-NMR分析结果一起,有力地支持催化体系多活性中心的结论。

乙丙共聚物及其共混物晶型探讨

用广角X-射线衍射(WAXD)和偏光显微镜(PLM)方法,研究了具有乙丙长序列乙丙共聚物及其共混物,发现通过熔融慢冷结晶样品,C_3含量在30mol％以上,衍射角2θ=20°处出现了属于γ-PP晶型的(140),(130)晶面衍射。含有乙丙长序列链结构的乙丙共聚物及共混物属(α+γ)混晶结构;含乙丙长序列的EPR以γ-相为主,嵌段物和共混物则以α-PP为主,形成γ-PP结构的必要条件是含有乙丙长序列链结构样品熔融慢冷结晶。

3,4-聚异戊二烯的磺化反应及其离聚体的结构研究

本工作合成了磺化的3,4-聚异戊二烯及其离子聚合体,IR和NMR谱图证明对3,4-聚异戊二烯的磺化反应是成功的,并且磺酸基团主要与3,4-链节的侧基双键发生反应。WAXD对磺化3,4-聚异戊二烯及其离聚体的研究表明,磺化度的增加使离聚体的结晶能力降低,SAXS结果表明,在离子含量为3.29mol％的离聚体中,未观察到离子簇聚集,只观察到多重离子对的散射。

尼龙-1010结晶结构

用WAXD方法测定了Nylon-1010为三斜晶系结晶结构;α=4.9(?),b=5.4(?),c=27.8(?),α=49°,β=77°,γ=63.5°,每个聚合物单胞含有一个重复单元,空间群为P(?)。模压试样用Ruland方法分析结晶度为60％。以上。电子密度相关函数法分析了SAXS现象,求得了Nylon-1010结晶片层厚度、过渡层厚度、长周期、比内表面及电子密度差。

聚苯胺晶性问题的探讨

用广角X射线衍射(WAXD),SEM,DSC和TGA方法研究了聚苯胺的晶性问题,结果表明,不同条件下所得聚苯胺其本征型的结晶行为差别较大。当聚合溶液的酸浓度在0.001～7N范围内时,随着酸浓度增加,其本征态聚合物的结晶性降低。所得产物的掺杂态较本征态更容易结晶,结晶度随掺杂剂浓度的升高而增加。适当的热处理可提高聚苯胺的结晶能力。

结晶聚合物的辐照效应——Ⅰ.尼龙-1010的聚集态结构对其辐射化学反应的影响

本文用DSC,WAXD,ESR和介电谱以及凝胶分数测定等技术,研究Nylon-1010的聚集态对γ-辐射化学反应以及辐照后热处理结果的影响。结果表明,辐照Nylon-1010的交联与裂解反应主要发生在非晶区或结晶表面,进一步证明了非晶区也是辐射后交联和后裂解主要反应区。

PP/EPO共混体系混容性与结晶结构

WAXD方法测定表明PP/EPO共混体系的结晶度随EPO组份含量的增加而降低,晶胞参数与组份比无关,并计算了第二类晶格畸变。根据PP/EPO的DSC和扭辫实验得出在所有组成下PP/EPO共混体系是不相容的。但在非晶区可能部分相容。

环氧树脂/聚氧化乙烯共混物及其与硫氰化钠络合物的结构研究(Ⅰ)

对不同分子量聚氧乙烯(PEO)以不同比例与双酚A二缩水甘油醚型环氧树脂(ER)制得的交联共混物ER/PEO,以及再与NaSCN络合后的产物用WAXD,SAXS,DSC和SEM等方法进行了研究,结果表明:随着ER含量的增加,ER/PEO共混物由晶态转为非晶态。ER/PEO属单斜晶系;与NaSCN络合后,体系结晶性变差。ER/PEO-NaSCN属三斜晶系,其长周期比相应ER/PEO交联共混物的长周期值大。EP的加入使非晶层增厚,结晶片层变薄,长周期值增加。

Composites of poly(ε-caprolactone) and Mo6S3I6 Nanowires

Composites of poly(e-caprolactone) (PCL) and molybdenum sulfur iodine (MoSI) nanowires were prepared using twin-screw extrusion. Extensive microscopic examination of the composites revealed the nanowires were well dispersed in the PCL matrix, although bundles of Mo6S3I6 ropes were evident at higher loadings. Secondary electron imaging (SEI) showed the nanowires had formed an extensive network throughout the PCL matrix, resulting in increased electrical conductivity of PCL, by eight orders of magnitude, and an electrical percolation threshold of 6.5T10S3vol%. Thermal analysis (DSC), WAXD, and hot stage polarized optical microscopy (HSPOM) experiments revealed Mo6S3I6 addition altered PCL crystallization kinetics, nucleation density, and crystalline content. A greater number of smaller spherulites were formed via heterogeneous nucleation. The onset of thermal decomposition (TGA) of PCL decreased by 70-C, a consequence of the thermal degradation of Mo6S3I6 to MoO3, which in turn accelerates the formation of volatile gases during the first stage of PCL decomposition.

Carbon nanotubes induced crystallization of poly(ethylene terephthalate)

We have investigated the crystallization characteristics of melt compounded nanocomposites of poly(ethylene terephthalate) (PET) and single walled carbon nanotubes (SWNTs). Differential scanning calorimetry studies showed that SWNTs at weight fractions as low as 0.03 wt% enhance the rate of crystallization in PET, as the cooling nanocomposite melt crystallizes at a temperature 10 °C higher as compared to neat PET. Isothermal crystallization studies also revealed that SWNTs significantly accelerate the crystallization process. WAXD showed oriented crystallization of PET induced by oriented SWNTs in a randomized PET melt, indicating the role of SWNTs as nucleating sites.

Mucoadhesive and elastic films based on blends of chitosan and hydroxyethylcellulose

Mucoadhesive polymeric films have been prepared based on blends of chitosan and hydroxyethylcellulose. The blends have been characterized by IR spectroscopy, DSC, WAXD, TGA, SEM, and mechanical testing. It is demonstrated that the mechanical properties of chitosan are improved significantly upon blending with hydroxyethylcellulose. An increase in hydroxyethylcellulose content in the blends makes the materials more elastic. The thermal treatment of the blends at 100 degrees C leads to partial cross-linking of the polymers and formation of water-insoluble but swellable materials. The adhesion of the films towards porcine buccal mucosa decreases with increasing hydroxyethylcellulose content in the blends.