用正电子湮没谱研究聚酯型聚氨酯的微观结构和自由体积特性  

MICRO-STRUCTURE AND FREE VOLUME PROPERTIES OF LINEAR POLYURETHANES MEASURED BY USING POSITRON ANNIHILATION SPECTROSCOPY

作　　者：宁超峰[1] 何春清[2] 张明[2] 胡春圃[1] 王波[2] 王少阶[2] 

机构地区：[1]华东理工大学材料科学与工程研究所,上海200237 [2]武汉大学物理系,武汉430072

出　　处：《高分子学报》2001年第3期299-305,共7页Acta Polymerica Sinica

摘　　要：用正电子湮没谱研究了两类分别由聚己二酸丁二醇酯多元醇和聚ε 己内酯多元醇合成的线型聚酯型聚氨酯 (PBU和PCU)在 140～ 36 0K温度范围内的结构转变和自由体积特性 .研究结果表明 ,两类聚氨酯(PU)在 140～ 36 0K温度范围内 ,都存在三个转变点 ,其中较低温度的转变 (约 2 0 0K)对应于PU中软段的玻璃化转变温度 (Tg) ,2 75K处的转变可能与样品吸附少量水分有关 ,较高温度的转变 (约 310K) ,对于PBU而言对应于软段结晶的熔点 ,而对于PCU则与在无序的硬段中混入一定量的软段后形成的相容区的Tg 有关 .当温度低于PU软段的Tg 时 ,两类PU的自由体积尺寸和浓度都随温度升高而增大 .当温度高于软段的Tg 但低于2 75K时 ,自由体积尺寸较快地增加 ,而自由体积浓度保持不变 .温度高于 2 75K并低于软段的熔点或硬段 软段相容区的Tg 时 ,自由体积尺寸增加速度最快 ,自由体积浓度却保持同样的数值 .当温度进一步升高时 ,自由体积尺寸和浓度都随温度增大而增加 .最后研究了这两类PU的自由体积分布与温度的关系 .所有这些实验现象均与大分子链的运动有关 。The structural transitions and free volume properties for two kinds of linear polyurethane prepared with polybutalene adipate polyol and polycaprolactone polyol (PBU and PCU) respectively were studied by means of positron annihilation spectroscopy in the temperature range from 140 K to 360 K,DSC and WAXD measurements. The experimental results indicated that there were three structural transition temperatures for these two polyurethanes (PUs) from 140 K to 360 K. The transition at low temperature (at around 200 K) was attributed to the glass transition temperature (T-g) of polyester soft segments existing in PU and the transition at 275 K could be related to the small amount water adsorbed in PU samples. The high temperature transition (at about 310 K) corresponded to the melting point of soft segment crystals in PBU and was also related to the T-g for compatible regions of the disordered hard segments with some soft segments existed in PCU. When the temperature was lower than the T-g of soft segments in PU,both the size and the relative concentration of free volume increased with increasing temperature for PBU and PCU. While the temperature was higher than the T-g of soft segmensts but lower than 275 K,the relative concentration of free volume reached a constant value but the size of free volume increased further. When the temperature was higher than 275 K but lower than the melting point of soft segment crystals or the T-g of hard/soft segment miscible regions,the relative concentration of free volume still kept constant but the size of free volume increased appreciably. When the temperature increased more, both the size and the relative concentration of free volume existing in PUs increased again. The distributions of free volume were also examined at various temperatures for these two PUs. All these experimental results could be related to the movement of macromolecular chains and the morphologies for these PUs measured by using DSC and WAXD.

关 键 词：线型聚酯型聚氨酯 正电子湮没谱 微观结构 自由体积 结晶 

分 类 号：O632[理学—高分子化学]