共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
Morphology of bisphenol A polysulfone-polyoxypropylene segmented copolymers was inves-tigated by means of differential scanning calorimetry and transmission electron microscopy. Theresults show that the molecular weights of the hard and soft segments have a pronounced effect onthe morphology of these segmented copolymers, which may changr from three-phase to single-phasestructure depending on the size and the relahve size of the segments. Heat treatment will enhancethe process of phase separation, increasing the domain size of the dispersed phase, Results obtainedby study on the dynamic mechanical properties of these copolymers well support the existence ofthree-phase morphological structure. 相似文献
3.
Taeyi Choi Kevin A. Masser Erica Moore Jadwiga Weksler Ajay Padsalgikar James Runt 《Journal of Polymer Science.Polymer Physics》2011,49(12):865-872
A novel macrodiol based on mixed silicone and carbonate chemistries was synthesized and used as a soft segment precursor in the synthesis of two series of segmented polyurethane (PU) copolymers varying in hard segment content and soft segment molecular weight. The hard segments in these copolymers were derived from 4,4‐methylene diphenyl diisocyanate and 1,4‐butane diol. The phase transitions, microphase separation behavior, and mechanical properties of the copolymers were investigated using a variety of experimental methods. When compared with segmented PU copolymers having predominately poly(dimethyl siloxane) soft segments, these siloxane–carbonate soft segment copolymers exhibit enhanced intersegment mixing, and consequently relatively low mechanical modulus. With relatively low modulus and siloxane units in the soft phase, the siloxane–carbonate PUs have potential for use in cardiac and orthopedic biomedical applications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 相似文献
4.
5.
L. A. Kiefer T. H. Yoon T. E. Glass S. K. Jayaraman J. E. McGrath 《Journal of polymer science. Part A, Polymer chemistry》1997,35(16):3495-3506
High molecular weight poly(dimethylsiloxane)/semicrystalline cycloaliphatic polyester segmented copolymers based on dimethyl-1,4-cyclohexane dicarboxylate were prepared and characterized. The copolymers were synthesized using a high trans content isomer that afforded semicrystalline morphologies. Aminopropyl-terminated poly(dimethylsiloxane) (PDMS) oligomers of controlled molecular weight were synthesized, end capped with excess diester to form a diester-terminated oligomer, and incorporated via melt transesterification step reaction copolymerization. The molecular weight of the polysiloxane and chemical composition of the copolymer were systematically varied. The polysiloxane segment was efficiently incorporated into the copolymers via an amide link and its structure was unaffected by low concentrations of titanate transesterification catalyst, as shown by control melt experiments. The homopolymer and copolymers were characterized by solution, thermal, mechanical, and surface techniques. The segmented copolymers were microphase separated as determined by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and by transmission electron microscopy (TEM). It was demonstrated that relatively short poly(dimethylsiloxane) segment lengths and compositions were required to maintain single phase melt polymerization conditions. This was, in fact, the key to the successful preparation of these materials. The copolymers derived from short poly(dimethylsiloxane) segments demonstrated good mechanical properties, melt viscosities representative of single phase polymer melts, and were easily compression molded into films. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3495–3506, 1997 相似文献
6.
7.
Doris Pospiech Liane Häußler Dieter Jehnichen Wolfram Kollig Kathrin Eckstein Karina Grundke 《Macromolecular Symposia》2003,198(1):421-434
The goal of the investigation presented here is the development of extremely hydrophobic materials based on polysulfone that can be applied, for instance, as fouling-resistant membrane materials. The concept used is the addition of semifluorinated polymers to polysulfone in suitable blend compositions. The influence of molecular parameters like chain structure of the semifluorinated polymer (segmented block copolymers, random copolymers) and segment molecular weight on the state of phase separation in the bulk and its influence on the surface properties have been systematically examined. It could be shown that segmented block copolymers with semifluorinated polyester segments with intermediate segment molecular weight are more suitable in blends with polysulfone than random polysulfone copolymers having semifluorinated side chains with respect to form homogeneous thin films (coatings) with highly non-wetting properties. 相似文献
8.
A novel class of segmented copolymers, dimethyldiphenylpolysiloxane/poly (oxytetramethylene)-polyurea (PSPEU), was synthesized from α, ω-bis (γ-aminopropyl) dimethyldiphenylpolysiloxane (APMPS), which was prepared by means of basic ring-opening copolymerization of octamethylcyclotetrasiloxane, hexaphenylcyclotrisiloxane and 1, 3-bis (γ-aminopropyl) tetramethyl disiloxane. The relationships between the diphenylsiloxy contents and the properties of APMPS, including refractive index, glass transition temperature, solubility parameter as well as thermal stability, were investigated; meanwhile, the thermal stability, dynamic mechanical properties, mechanical properiesas well as the antithrombogenicity in vitro of the PSPEU were also revealed. 相似文献
9.
10.
Carboxyl vinyl terminated polytetrahydrofuran macromers and telechelic oligomers were synthesized from hydroxyl terminated polytetrahydrofuran by end group conversion. From these macromers or telechelic oligomers and styrene polytetrahydrofuran/polystyrene segmented and graft copolymers were synthesized and the effects of molecular structure on the damping properties of those copolymers were also studied. 相似文献
11.
新型含有机硅二元多嵌段共聚物的研究 总被引:1,自引:0,他引:1
报道了聚羟基醚(PHE)、聚羟基醚砜(PHES)、酚酞聚羟基醚(PPHE)和聚对羟基苯乙烯(PHS)与端胺基聚二甲基硅氧烷(PDMS)通过羟胺缩合生成ABmn新型结构的可溶性含有机硅二元多嵌段共聚物,m值在1~6之间,详细讨论了反应物浓度对共缩聚反应的影响,并通过分子量测定、红外光谱分析和动态力学分析(DMA)技术初步确定了其反应机理、结构和动态力学性能. 相似文献
12.
从不同结构层次角度说明了多嵌段共聚物的分子组成不均一性。提出了一种新的看法,即在讨论多嵌段共聚物的形态和性能时,除了链段间的微相分离外,还必须首先考虑不同平均链段长度的多嵌段大分子间的宏观相分离作用。如何表征与控制其组成不均一性是十分重要的课题。 相似文献
13.
14.
聚酯聚氨酯嵌段共聚物及其离聚体的研究 总被引:1,自引:0,他引:1
以烃基封端的聚酯与4,4'-二苯基甲烷二异氰酸酯及N-甲基二乙醇胺合成了3种不同硬段含量的聚酯聚氨酯嵌段共聚物。然后,与γ-丙磺酸内酯反应,制得不同离子化程度的离聚物。通过对这些聚合物进行红外光谱、应力-应变试验、差示扫描量热(DSC)、动态力学性能和介电温度谱的分析,得出硬段含量和离子化程度对材料微相分离和物理性能的影响规律,并探讨了引起材料微观形态变化的原因。 相似文献
15.
De-zhu Ma Dong-sheng Li Ming-chuan Zhao Mo-zhen Wang Ran Ye Xiao-lie Luo Department of Polymer Science Engineering University of Science Technology of China Hefei China 《高分子科学》1999,(3):271-280
A series of ethylene oxide-butylene terephthalate (EOBT) segmented copolymers with differentsoft segment length and hard segment content were synthesized. The compositional heterogeneity was studiedby solvent extraction. The results show that the compositional heterogeneity increases when soft segmentlength and hard segment content increase. The compositional heterogeneity is also reflected in thecrystallization behavior and morphology of soft and hard segment in EOBT segmented copolymer. The morecompositional heterogeneous the EOBT segmented copolymer is, the more different the morphology and thecrystallization behavior between separated fractions. Compared with ethylene oxide-ethylene terephthalate(EOET) segmented copolymer, compositional heterogeneity in EOBT segmented copolymer is weaker. Butthe compositional heterogeneity in EOBT segmented copolymer with long soft segment and high hardsegment content is still obvious. 相似文献
16.
Segmented polyesteramides have been synthesized from N,N'-bis(p-carbomethoxybenzoy)butanediamine(T4T)as crystalline segments and mixture of poly(tetramethylene oxide)with the average molecular weight 1000(PTMO1000)and 1,5-pentanediol(PDO)as soft segments. The polymerization was carried out in the melt at 250℃ for 1-2 h while vacuum was applied. The chemical composition of the copolymer was measured by H1-NMR. The melting behavior of the copolymers was studied by the differential scanning calorimeter. The dynamic mechanical properties were investigated on injection moulded bars by means of dynamic mechanical analysis. It was found that the copolymers with more than 40% molar ratio PDO showed two glass transition temperatures and two melting temperatures. The glass transition temperatures are independent of composition,and thus two fully phaseseparated amorphous phases are present. The melting temperatures change with PDO content. The amount of PDO has an effect on both TmA and TmB . TmA is attributed to the lamella consisting of extended T4T segments,while TmB results from the much thicker lamella consisting of both extended T4T and PDO segments. It is also possible that some PDO is present in the interphase as adjacent re-entry groups. So the resultant copolymer shows that a complex system,two crystalline phases,two amorphous phases and an interphase are involved in the copolymer. The undercooling for these copolymers is small,which means that these segmented copolymers crystallize fast. 相似文献
17.
Debby Husken 《European Polymer Journal》2008,44(1):130-143
The synthesis and characterisation of segmented block copolymers based on mixtures of hydrophilic poly(ethylene oxide) and hydrophobic poly(tetramethylene oxide) polyether segments and monodisperse crystallisable bisester tetra-amide segments are reported. The PEO length was varied from 600 to 8000 g/mol and the PTMO length was varied from 650 to 2900 g/mol. The influence of the polyether phase composition on the thermal mechanical and the elastic properties of the resulting copolymers was studied.The use of high melting monodisperse tetra-amide segments resulted in a fast and almost complete crystallisation of the rigid segment. The copolymers had only one polyether glass transition temperature, which suggests that the amorphous polyether segments were homogenously mixed. Thermal analysis of the copolymers showed one polyether melting temperature that was lower than in the case of ideal co-crystallisation between the two polyether segments. However, at PEO or PTMO lengths larger than 2000 g/mol two polyether melting temperatures were observed. The copolymer with the best low temperature properties was based on a mixture of PEO and PTMO segments, both having a molecular weight of 1000 g/mol, at a weight ratio of 30/70. 相似文献
18.
The compositional heterogeneity of two impact polypropylene copolymers(IPCs) was studied by a combinatory investigation of temperature rising elution fractionation(TREF) and solvent fractionation.The chain structures and composition of fractions obtained from solvent fractionation were examined in detail.The TREF results shows that there are much more E-P segmented copolymer and more uniform distribution of ethylene sequence in IPC-1,which is responsible for its better comprehensive mechanical performance.The fractions from hexane and heptane are ethylene-propylene rubber phase and E-P block copolymers respectively.The result of solvent fractionation method also shows that custom hexane or heptane extractions can not extract the E-P copolymer completely. 相似文献
19.
M. E. Rogers T. E. Glass S. J. Mecham D. Rodrigues G. L. Wilkes J. E. McGrath 《Journal of polymer science. Part A, Polymer chemistry》1994,32(14):2663-2675
New strategies for the synthesis of perfectly alternating segmented polyimide-polydimethyl siloxane copolymers were developed by utilizing a transimidization method. Imide oligomers endcapped with 2-aminopyrimidine were reacted with aminopropyl terminated (dimethyl siloxane) oligomers to afford perfectly alternating segmented imide siloxane copolymers. The polymerization was conducted in solvents such as chlorobenzene and chlorofrom. High molecular weight, fully imidized perfectly alternating segmented imide siloxane copolymers were obtained within 2 h at temperatures of 60-110°C. The mechanism of the reaction was further elucidated via model compounds and NMR characterization. The block copolymers exhibited two Tgs due to the microphase separation of the polyimide and polysiloxane phases. The Tg of the polyimide phase was a function of the length of the polyimide block. However, partial phase mixing was also evident from the DSC results on the imide siloxane copolymers prepared with low molecular weight polyimide segments. Thermooxidative stability and tensile properties of the perfectly alternating segmented imide siloxane copolymers were found to be principally dependent on the amount of poly (dimethyl siloxane) incorporated in the copolymer and did not correlate with the poly (dimethyl siloxane) or polyimide block lengths. The stress-strain behavior of both solvent cast films or molded films is also reported. © 1994 John Wiley & Sons, Inc. 相似文献
20.
A series of novel poly(trimethylene terephthalate)-block-poly(tetramethylene oxide) (PTT--PTMO) segmented block copolymers were synthesised by transesterification in the melt of dimethyl terephthalate, 1,3-propanediol and poly(tetramethylene oxide) glycol (PTMO, 1000 g/mol). A range of multiblock copolymers were synthesized, with flexible PTMO segments contents varying from 20 to 80 wt%. The novel poly(ether-block-ester)s were characterized by using viscometry, hardness measurements, differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and tensile properties. 相似文献