新的液晶性壳聚糖衍生物——氰乙基壳聚糖的合成与表征

甲壳素是自然界蕴藏量最丰富的天然高分子化合物之一,但人们对它的了解却远不如纤维素和淀粉.仅就液晶领域而言,纤维素衍生物的液晶性早已为人们所认识,例如氰乙基纤维素的液晶性已有很多研究.     

生物高分子液晶的新家族——甲壳素及其衍生物

讨论了生物高分子甲壳素及其衍生物形成液晶态的基本结构条件。简要介绍了为制备液晶性甲壳素衍生物所必须的一些主要的化学修饰途径。综述了十几年来甲壳素衍生物（主要是壳聚糖及其衍生物）液晶性的研究进展。介绍了甲壳素及其衍生物的液晶纺丝及其应用前景。指出甲壳素衍生物已成为纤维素之外生物高分子液晶的一个新的大家族。     

一种新的液晶高分子——丁酸壳聚糖的合成与表征

甲壳素几乎不溶于任何溶剂,由于其脱乙酰化产物壳聚糖含自由氨基,能被酸质子化而溶解,所以壳聚糖的应用领域远多于甲壳素.但是壳聚糖也仅能溶于酸性介质中,并不能溶于纯水和普通有机溶剂,因而人们对甲壳素或壳聚糖进行各种化学改性[1,2],寻求溶解性更好尤其能溶于水的衍生物,以扩大其应用范围.本文按文献[2～4]方法合成了O-丁酰化壳聚糖(简称丁酸壳聚糖),首次报道它具有溶致液晶性.     

壳聚糖/二氯乙酸溶致液晶的热致相转变

关于壳聚糖及其各种衍生物的溶致液晶的研究已有报道^[13],但尚未见到有关壳聚糖/有机酸液晶溶液的热致相转变的报道.本文研究了壳聚糖/二氯乙酸液晶溶液的相转变,并探讨了该体系的相转变机理.     

甲壳素——一类新的液晶性多糖

"将甲壳素的结构与纤维素进行了比较, 并根据结构和链刚性指出其形成液晶态的可能性。简要介绍了制备液晶性甲壳素衍生物所必须的一些主要的化学修饰途径。叙述了15 种甲壳素衍生物的溶致液晶行为以及结构因素对它们液晶临界行为的影响。介绍了甲壳素衍生物形成的主要液晶态织构, 如指纹状织构、交替偏振场织构、条带织构和滴状织构, 以及甲壳素衍生物? 二氯乙酸溶液的热致相转变。综述了甲壳素的成纤性和液晶纺丝。     

羧甲基壳聚糖对亚铁离子的吸附

壳聚糖是由甲壳素经脱乙酰基后得到的一种天然高分子氨基多糖 ,它是金属离子的良好配体 ,其配合物在工业、农业、食品、环保、医药等方面的应用已有许多研究 [1～ 4 ] .脱乙酰基后的壳聚糖溶解性有很大改善 ,但仍只能溶于酸或酸性水溶液 ,限制了它的推广应用 .通过化学改性的羧甲基壳聚糖 ( CMCS)具有良好的水溶性、保湿性、乳化性 ,其分子中含有— OH、— NH2 、—COOH等基团 ,能有效络合金属离子 [5] .人体对壳聚糖 -亚铁络合物的吸收远远大于传统的 Fe SO4 药物 [6 ] ,壳聚糖及其衍生物与 Fe2 的络合物有可能用于治疗缺铁性贫血 …     

粘度法预测聚乙二醇/壳聚糖体系的相容性

甲壳素在自然界的含量很大，仅次于纤维素，是一种颇具应用潜力的天然高分子．可由甲壳素经脱酸基化制得壳聚糖．由于其分子中存在氨基，因此能溶解干酸性水溶液中，并以聚电解质的形式存在，近来用壳聚糖制得的纤维膜应用于药物、食品等的分离和纯化、污水的处理，分离效果好，且不带入任何化学杂质．在壳聚糖纤维膜制作及与纤维的混纺过程中，都要探讨它与其它相应高聚物的相容性[1]．我们以相容的壳聚糖（chitosan）／聚乙二醇（PEG）体系为例，采用粘度法讨论其分子间的相互作用，并预测它们的相容性．壳聚糖的基本结构为1实验部分1.1…     

热塑性淀粉中氢键及其对性能的影响

热塑性淀粉中的氢键对热塑性淀粉的性能有决定性的作用．本文利用红外光谱分析甘油或甲酰胺塑化热塑性淀粉中塑化剂和淀粉间的氢键形成情况，发现在淀粉中，与塑化剂形成氢键的主要是C-O-C基团中的氧原子和C-O-H基团中的氢原子；而且过量的塑化剂之间会形成氢键，减弱塑化剂与C-O-C中氧原子的氢键作用．与甘油相比，甲酰胺可以和淀粉形成更稳定的氢键．X-ray衍射研究了氢键对两种热塑性淀粉在不同湿度环境下的回生性能的影响．结果表明甲酰胺可以有效抑制淀粉回生．热动态力学分析(DMTA)研究发现，氢键使甲酰胺塑化热塑性淀粉的玻璃化转变温度更低．氢键使甲酰胺塑化热塑性淀粉强度和杨氏模量低，但伸长率和断裂能大．     

新的溶致液晶性高分子——N-马来酰化壳聚糖的合成与表征

新的溶致液晶性高分子——Ｎ┐马来酰化壳聚糖的合成与表征董炎明李志强（厦门大学化学系福建厦门３６１００５）壳聚糖（（１，４）－２－氨基－２－脱氧－β－Ｄ－葡聚糖）是甲壳素经脱乙酰化得到的一种生物高分子。它的原料是海产品加工厂的废料，因而来源十分丰富，作...     

甾体枝化的壳聚糖液晶合成及其表征

利用壳聚糖分子内的氨基易于进行化学反应的特点,让壳聚糖分子上的氨基与脱氧胆酸上的羧基团连接.由于脱氧胆酸本身是手性的结构,借此探索甾体枝化对壳聚糖液晶的影响.使用红外光谱研究其结构;使用热失重分析仪研究其热性质,并通过偏光显微镜研究了甾体枝化的壳聚糖的液晶性,表现为溶致胆甾型液晶.对壳聚糖进行改性的同时增加了其溶解性和功能性.     

Preparation and characterization of biodegradable poly(l-lactide)/chitosan blends

In order to improve the properties of chitosan and obtain new fully biodegradable materials, blends of poly(l-lactide) (PLLA) and chitosan with different compositions were prepared by precipitating out PLLA/chitosan from acetic acid-DMSO mixtures with acetone. The blends were characterized by Fourier transform infrared analysis (FTIR), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), ¹³C solid-state NMR and Wide-angle X-ray diffraction (WAXD). FTIR and XPS results showed that intermolecular hydrogen bonds existed between two components in the blends, and the hydrogen bonds were mainly between carbonyls of PLLA and amino groups of chitosan. The melting temperatures, cold crystallization temperatures and crystallinity of the PLLA component decreased with the increase in chitosan content. Blending chitosan with PLLA suppressed the crystallization of the PLLA component. Although the crystal structure of PLLA component was not changed, the crystallization of the blends was affected because of the existence of hydrogen bonds between two components, which was proved by WAXD results.     

邻苯二甲酰化壳聚糖的合成与溶致液晶表征

从全脱乙酰化壳聚糖出发,在室温下合成了一系列不同取代度的邻苯二甲酰化壳聚糖(PhCS),由于反应条件温和,产物未发生进一步的酰亚胺化.X射线电子能谱(XPS)被用来测定PhCS的取代度.测定结果表明在N上和O上均发生取代,N上反应的取代度随酸酐用量的增加基本保持不变(0.26±0.03),而O上的取代度却不断变大(0.01～1.54),合成产物的总取代度为0.26～1.81.邻苯二甲酰化壳聚糖可溶解于普通的有机溶剂,如DMSO、二氯乙酸和甲酸,并形成溶致液晶.测定了PhCS在这些溶剂中的临界浓度(c),结果表明c基本上不受取代度变化的影响.     

甲壳素类液晶高分子的研究Ⅷ. N-邻苯二甲酰化壳聚糖/DMSO液晶溶液的热致相转变

合成了氮上完全取代的邻苯二甲酰化壳聚糖 (PhthCS) .用DSC研究了PhthCS DMSO液晶溶液的热致相转变 .偏光显微镜和DSC测定都表明临界浓度为 43wt% .在浓度高于 43wt%的溶液的DSC曲线中观察到了除了液晶 各向同性液体转变 (清亮点 )外还有一个明显的凝胶 溶胶转变 .凝胶 溶胶转变温度和转变焓均比文献报道的不规则取代的N 邻苯二甲酰化 O 乙酰化壳聚糖大得多 ,可见取代的规整性对凝胶 溶较转变有很大的影响 .根据DSC研究结果绘制了PhthCS DMSO体系的相图     

Thermal decomposition of p-methyl-p'-nitrobenzoyl and bis-p-nitrobenzoyl peroxides

Differential enthalpic analysis was carried out below the melting point as well as at regular increases of temperature over the melting point of peroxides. From these measurements it follows that the thermal stabilities of peroxides in the solid state increase with their melting points. The rise in the melting point of the peroxide due to changed chemical structure is accompanied by a rise in the melting points of products which in turn affects the isothermal autocatalytic decomposition. The common feature of the thermal decomposition of the peroxides studied below their melting points is a very high apparent activation energy of the initiation of a chain decomposition reaction which is several times higher than that of a spontaneous thermal decomposition of peroxide in solution or in a melt of peroxide. p]From the study of the decomposition of nitro derivatives of benzoyl peroxide in solution it is known¹ that the electron attracting nitro-substituents have a retarding effect on the spontaneous decomposition of peroxides. The introduction which accompanies its thermal decomposition in solution². However not only the substitution of nitro groups in the molecule but also the presence of nitro compounds accelerates the decomposition of benzoyl peroxide³. This indicates that the decomposition reaction may be influenced not only by an intramolecular rearrangement of electrons but also by an intermolecular interaction of nitro compounds with the peroxidic compounds or radicals generated by them. The substitution of methyl groups for hydrogen in aromatic rings does not produce any marked changes in the decomposition reactions of benzoyl peroxide². p]Among other changes produced by substitution, the physical changes—in particular, the changes in the melting points of investigated substances—are of importance to out study of the thermal decomposition of nitro derivatives of nitro derivatives of benzoyl peroxide. These data are interesting mainly because the decomposition of peroxides is influenced by the state of aggregation of the decomposing substances.     

氰乙基羟丙基壳聚糖的溶致和热致液晶性研究

从壳聚糖出发先羟丙基化再氰乙基化,合成了氰乙基羟丙基壳聚糖(羟丙基的摩尔取代度为3.2,氰乙基的取代度为1.0).氰乙基羟丙基壳聚糖(CNHPCS)和羟丙基壳聚糖(HPCS)两者都有胆甾型溶致液晶性,浓溶液呈现指纹状织构.在二氯乙酸中,前者的临界浓度(29%,质量分数,下同)高于后者(17%).这一结果可以用引入氰乙基增加了分子间作用力从而使得链刚性增加来解释.CNHPCS在熔点193℃和分解温度220℃之间很窄的温区内观察到有热致液晶胆甾相.CNHPCS固体膜的胆甾相螺距采用激光小角光散射法测定,结果与偏光显微镜测得的数值一致.     

N-对甲基苯基-N′-（2-吡啶基）脲的低温热容及热分析

通过低温量热和热分析方法,测定了N-对甲基苯基-N′-（2-吡啶基）脲(以下简称NPMPN′2PU)的低温热容和热力学性质.通过对NPMPN′2PU进行低温量热,得到了NPMPN′2PU在80～370 K 温区的热容曲线,热容曲线光滑,没有任何热异常现象,由此实验热容数据计算出NPMPN′2PU在这段温区内的热力学数据.从DSC实验结果发现, NPMPN′2PU熔化峰值出现在173.86 ℃,熔化焓为204.45 kJ•mol－1.紧接熔化峰后NPMPN′2PU开始分解,分解峰只有一个,分解峰值温度为226.11 ℃.TG和DTG的实验结果表明,NPMPN′2PU失重的峰值为227.2 ℃,这些结果与DSC实验结果吻合.     

Biodegradable aliphatic/aromatic copolyesters based on terephthalic acid and poly(L-lactic acid): Synthesis, characterization and hydrolytic degradation

<正>Biodegradable aliphatic/aromatic copolyesters,poly(butylene terephthalate-co-lactate)(PBTL) were prepared via direct melt polycondensation of terephthalic acid(TPA),1,4-butanediol(BDO) and poly(L-lactic acid) oligomer(OLLA). The effects of polymerization time and temperature,as well as aliphatic/aromatic moiety ratio on the physical and thermal properties were investigated.The largest molecular weight of the copolyesters was up to 64100 with molecular weight distribution index of 2.09 when the polycondensation was carried out at 230℃for 6 h.DSC,XRD,DMA and TGA analysis clearly indicated that the degree of crystallinity,glass-transition temperature,melting point,decomposition temperature, tensile strength,elongation and Young's modulus were influenced by the ratio between TPA and OLLA in the final copolyesters.Hydrolytic degradation results demonstrated that the incorporation of biodegradable lactate moieties into the aromatic polyester could efficiently improve hydrolytic degradability of the copolymer even though it still had many aromatic units in the main chains.     

The effect of γ rays upon monohydrated asparagine. A DSC study

Crystalline non-irradiated and irradiated monohydrated asparagine was investigated by means of DSC. The samples were irradiated at room temperature with gamma radiations using a ¹³⁷Cs source. The exposure doses ranged between 1 and 12 kGy. All samples were scanned in non-sealed pans, from room temperature to a temperature beyond the melting point. The change of registered DSC thermograms for the irradiated samples compared to those of non-irradiated ones and the variation of the parameters associated to dehydration and melting—decomposition with the cumulative dose were analyzed. The study has put in evidence transformations related to the values of characteristic temperatures of peaks and to the thermal effects. The diffusion and desorption of water molecules is hindered by the free radicals formed by irradiation. The most stable free radical species is formed by the extraction of a hydrogen atom from the methylene group of the amino acid chain, done by another hydrogen atom, probably derived from a water molecule.     

Study on the decomposition kinetics of FOX-7 and HNF

At TNO Prins Maurits Laboratory the characterisation and application of energetic materials is one of the main research topics. In this respect, the activities are focussed on using thermal analysis techniques such as TG/DTA and DSC. Standard DSC and TG/DTA techniques usually apply a linear temperature increase. During this gradual temperature change, the sample may pass certain phase changes related to different crystal structures, followed by a melting/decomposition of the material. In this way physicochemical properties like phase change temperatures, melting point, enthalpy of melting, decomposition temperature, etc. can be determined. By applying different heating rates, an analysis of the decomposition kinetics can be performed as well, which gives additional information on the decomposition process of the material. In this way the activation energy of the decomposition process and the 'shelf-life' of the material, when stored at a certain temperature, can be assessed. In a co-operation with the Technical University of Aachen, two relatively new and promising energetic materials were investigated: FOX-7 and HNF. FOX-7, or 1,1-diamino-2,2-dinitroethylene, is a less sensitive explosive, which could find application as a substitute of RDX (less sensitive but with preservation of performance). Hydrazinium nitroformate (HNF) is an oxidiser with potential use as a high-performance, chlorine-free ingredient in rocket propellants. The results of the TG/DTA and DSC tests, as well as the results of the analysis of the decomposition kinetics of these two materials, will be reported and discussed in this paper. This revised version was published online in July 2006 with corrections to the Cover Date.     

Plasticization and cocrystallization in LLDPE/wax blends

The structure and thermal properties of linear low‐density polyethylene (LLDPE)/medium soft paraffin wax blends, prepared by melt mixing, were investigated by differential scanning calorimetry (DSC) and small‐ and wide‐angle X‐ray scattering (SAXS and WAXS). The blends form a single phase in the melt as determined by SAXS. Upon cooling from the melt, two crystalline phases develop for blends with more than 10 wt % wax characterized by widely different melting points. The wax acts as an effective plasticizer for LLDPE, decreasing both its crystallization and melting temperature. The higher melting point crystalline phase is formed by less branched LLDPE fractions. On the other hand, the lower melting point crystalline phase is a wax‐rich phase constituted by cocrystals of extended chain wax and short linear sequences of highly branched LLDPE chains. The presence of cocrystals was evidenced by standard DSC results, successive self‐nucleation and annealing (SSA) thermal fractionation and by the detection of a new SAXS signal attributed to the lamellar long period of the cocrystals. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1469–1482