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排序方式: 共有218条查询结果,搜索用时 15 毫秒
61.
合成了一种可在结肠部位被特异酶解的两亲性嵌段高分子,由聚丙交酯(PLA)疏水嵌段和聚乙二醇(PEG)亲水嵌段组成,两者通过5,5′-偶氮二水杨酸(OLZ)偶联,其中的偶氮键可被结肠部位的偶氮还原酶特异酶解.利用FTIR、NMR和GPC等方法表征了共聚物的结构,并通过透射电镜(TEM)和动态光散射(DLS)等方法研究了该高分子载体在水溶液中的组装行为.结果表明MPEG-OLZ-b-PLA可在水介质中形成尺寸在30nm左右的球形胶束,并在大鼠全盲肠提取液中被特异性酶解。 相似文献
62.
《Composite Interfaces》2013,20(4-6):307-317
On the basis of the stereocomplex formation between poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA), the stereocomplexation-induced surface properties of enantimeric polylactide blends were inverstigated by electron spectrometer for chemical analysis (ESCA) and contact angle measurements as a function of a degree of complexation. The complexation of blends was controlled by using the stereochemical polylactides (stPLAs) with percent D repeat unit contents (optical purity) of 100, 98, 95, 90, and 85%. The PLLA-b-poly(dimethyl siloxane) (PDMS)-b-PLLA triblock copolymer, instead of PLLA was used as a surface probe material because of the high surface segregation of PDMS blocks. From ESCA measurements, the surface segregation of PDMS of PLLA-b-PDMS-b-PLLA/stPLA blends with ≤10% optical impurity was rapidly decreased with a degree of complexation. However, the uncomplexed blends >10% optical impurity showed that the surface segregation of PDMS was nearly that of PLLA-b-PDMS-b-PLLA. Similar behaviors were observed in the contact angle measurements. These results indicate that 10% optical impurity is a critical value at which the complex formation and the surface properties of the PLLA-b-PDMS-b-PLLA/stPLA blends can be controlled. 相似文献
63.
PLA大分子单体接枝NVP共聚物的合成与性能 总被引:2,自引:0,他引:2
制备了末端为双键的功能化聚乳酸大分子单体(PLA-HEMA),并以此大分子单体与N-乙烯基吡咯烷酮(NVP)进行自由基溶液共聚,合成了具有亲水性PVP-PHEMA主链和疏水性PLA支链的接枝共聚物。用FT-IR1、H-NMR、GPC、DSC、表面接触角测定研究了共聚物的结构与性能。结果表明:共聚物为非晶聚合物;NVP的摩尔投料量对共聚物的性能有显著影响,随NVP投料量增大,共聚物的分子量有所下降,玻璃化转变温度(Tg)增大;由于亲水性PVP和PHEMA链段的引入,共聚物的亲水性优于相应的线型聚乳酸材料。 相似文献
64.
本文提出了克服PLA固定容量的限制,扩展逻辑综合能力的两种技术:一是在改用带二位译码器PLA的情况下,减少函数乘积项的算法;二是将逻辑函数修改技术用于PLA的逻辑综合技术。 相似文献
65.
Eric Bryan Bond 《Macromolecular Symposia》2003,197(1):19-32
The fiber spinning behavior of a poly(3-hydroxyalkanoate) (PHA) copolymer resin containing 11.3 mol% hexanoate copolymer (H11) was studied to determine its usefulness in fiber based applications, such as nonwovens. Monocomponent fibers were spun initially, but it was found they would not solidify in the spinline. Bicomponent (sheath/core) fibers were melt spun using a H11 core and a polylactic acid (PLA), as well as a polyethylene succinate (PES) sheath. The spinning results showed that H11 levels up to 30wt% could be incorporated with stable spinning. The incorporation of H11 was found to be limited due to the slow crystallization kinetics of the H11 in the spinline. The neat and bicomoponent fibers were found to have tensile strengths similar to polypropylene. The PES based fiber compositions were found to have elongation-at-break values similar to PP. Neat H11 copolymer fibers were found to be readily biodegradable at 25°C under aerobic conditions. 相似文献
66.
WANG Li-qun~ 《高等学校化学研究》2001,17(3):334-337
Starch is the second largest natural biopolymer. Its unique biodegradable and biocompatible properties make it be increasingly applied to the field of biomedicine. As one kind of polysaccharide, starch is easily degraded into small organic molecules by amylase in the alimentary canal. The fact that the activity of amylase is restrained in the high acid environment in stomach provides an opportunity to prepare an intestinal-specific delivery carrier with 相似文献
67.
End-stage renal diseases are affecting many patients and as a result, demand to receive dialysis service is growing annually. Morbidity and mortality rates are reported to be higher in comparison with healthy humans. The reason is reported to be the hemoincompatiblity of blood purification membranes, which hinders patients’ lives. Activation of different immune systems in the body, in case of blood-membrane interaction, results in several side effects, of which cardiovascular shocks have been mentioned to be a major one. Efforts to solve this issue have resulted in different generations of dialysis membranes. Zwitterionic immobilized membranes are the latest (third) generation, which owns a higher degree of hemocompatiblity with more stability of immobilized structures. This critical review intends to cover recent efforts conducted over the zwitterionization of polymeric membrane surfaces with the goal of improving hemocompatibility. Different aspects of third-generation membranes are discussed for a better understanding of the current gap and gathering the knowledge to further develop the field. Accordingly, this critical survey provides an in-depth understanding of blood purification membranes zwitterionization for paving the way for the optimum enhancement of hemodialysis membrane hemocompatibility. 相似文献
68.
聚乳酸/聚氨酯共混体系相容性研究 总被引:2,自引:1,他引:2
采用热塑性聚氨酯弹性体(TPU)作为改性剂来增韧聚乳酸(PLA),通过溶度参数法、聚合物混合焓变法预测了TPU和PLA的相容性,并且通过稀溶液粘度法、动态热机械分析(DMA)及扫描电镜(SEM)对两者相容性进行表征,结果显示PLA和TPU为部分相容体系.共混溶液的粘度与组成含量的变化呈非线性关系;PLA/TPU共混膜的... 相似文献
69.
70.