Thermoplastic segmented polyurethanes (PUs) can exhibit shape memory behavior, if they feature multiple kinds of physical cross-links that can be dissociated at different temperatures. This is the case if the hydrogen-bonded hard phase is joined with soft segments that can partially crystallize, so that the melting transition acts as the memory switch. For applications in the biomedical field, it is important that the fixation and recovery temperatures can be minutely controlled. We show here that this tailoring can be easily achieved by formulating a commercial PU featuring poly(1,4-butylene adipate) (PBA) as a crystallizable segment (PBA-PU) with either PBA or poly(ε-caprolactone) (PCL) of moderate molecular weight. We show that the nature of the end groups and the processing conditions dictate if there is any reaction between the components or if the product is merely a blend. Interestingly, in either case, the addition of PBA or PCL causes nucleation and thereby a noteworthy increase of the crystallization temperature of the switching element from below to above ambient temperature, so that excellent shape fixity (∼98%) can be achieved at 37 °C. The melting temperature is maintained above 50 °C and significant increases in strength and modulus are achieved. The new materials platform is well suited for applications in which a shape is to be fixed at physiological temperature.

中文翻译：

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通过共混调整分段聚酯（聚氨酯）的形状记忆性能

如果热塑性嵌段聚氨酯（PU）具有多种可以在不同温度下解离的物理交联键，则它们会表现出形状记忆性能。如果氢键结合的硬相与可以部分结晶的软链段连接，则情况就是这样，以便熔融转变充当记忆开关。对于生物医学领域的应用，重要的是可以精确控制固定和恢复温度。我们在这里表明，可以通过配制以聚（1,4-己二酸丁二酯）（PBA）为可结晶链段（PBA-PU）与PBA或聚（ε-己内酯）（PCL）的商业PU来轻松实现这种剪裁中等分子量。我们表明，端基的性质和加工条件决定了组分之间是否有任何反应或产物仅仅是混合物。有趣的是，无论哪种情况，添加PBA或PCL都会导致成核，从而使开关元件的结晶温度从低于环境温度明显升高到高于环境温度，从而在37°C时可获得出色的形状固定性（〜98％）。 C。熔融温度保持在50°C以上，强度和模量显着提高。新材料平台非常适合将形状固定在生理温度下的应用。添加PBA或PCL会导致成核，从而使开关元件的结晶温度从低于环境温度明显升高到高于环境温度，因此在37°C时可获得出色的形状固定性（约98％）。熔融温度保持在50°C以上，强度和模量显着提高。新材料平台非常适合将形状固定在生理温度下的应用。添加PBA或PCL会导致成核，从而使开关元件的结晶温度从低于环境温度明显升高到高于环境温度，因此在37°C时可获得出色的形状固定性（约98％）。熔融温度保持在50°C以上，强度和模量显着提高。新材料平台非常适合将形状固定在生理温度下的应用。