Thermoplastic elastomers based on strong and well-defined hydrogen-bonding interactions
Thermoplastic elastomers based on strong and well-defined hydrogen-bonding interactions
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DOI：
10.1021/ma800744c
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发表时间：
2008-08-12
期刊：
影响因子：
5.5
通讯作者：
Baaijens, Frank P. T.
中科院分区：
文献类型：
--
作者：
Sontjens, Serge H. M.;Renken, Raymond A. E.;Baaijens, Frank P. T.
为了研究强且定义明确的氢键对热塑性弹性体（TPE）性能的影响，我们采用了两种不同的且强二聚的2-脲基-4-[1H]嘧啶酮（UPy）四重氢键单元作为物理交联剂。虽然UPy基团因此在这些TPE中用作“硬相”或“硬嵌段”，但无定形聚酯已被用作“软相”或“软嵌段”。UPy单元侧接有空间要求高的异佛尔酮间隔基或线性异佛尔酮，其中这些间隔基分别衍生自异佛尔酮二异氰酸酯（IPDI）或异佛尔酮二异氰酸酯（HDI）。分子水平上的这种差异导致IPDI情况下的均匀无定形材料（聚合物1）和HDI情况下的纳米相分离材料（聚合物2），如AFM和DSC实验所揭示的。除了形态和纳米组织的这种独特差异外，两种材料的宏观性质也有根本不同。在线性应力-应变和DMTA实验中，均质IPDI材料1在室温下显示出类似橡胶的行为，而机械性能强烈依赖于温度。纳米相分离的HDI材料2显示出橡胶和塑性行为的组合，并且在0和50摄氏度之间显示出清晰的橡胶平台，几乎没有温度依赖性。用多频DMTA法测得后者的表观流动活化能为135 kJ mol（-1）。
In order to investigate the effects of strong and well-defined hydrogen bonding on the properties of thermoplastic elastomers (TPEs), we have applied two distinct and strongly dimerizing 2-ureido-4-[1H]pyrimidinone (UPy) quadruple hydrogen-bonding units as physical cross-linker. While the UPy groups consequently serve as the "hard phase" or "hard block" in these TPEs, an amorphous polyester has been used as the "soft phase" or "soft block". The UPy unit has been flanked with either a sterically demanding isophorone spacer or a linear hexamethylene, where these spacers have been derived from isophorone diisocyanate (IPDI) or hexamethylene diisocyanate (HDI), respectively. This difference on a molecular level leads to a homogeneous amorphous material in the IPDI case (polymer 1) and to a nanophase-separated material in the HDI case (polymer 2) as revealed by AFM and DSC experiments. Apart from this distinctive difference in morphology and nanoscopic organization, the macroscopic properties of both materials are also fundamentally different. In linear stress-strain and DMTA experiments, the homogeneous IPDI material 1 shows rubberlike behavior at room temperature, while the mechanical properties are strongly temperature dependent. The nanophase-separated HDI material 2 shows a combination of rubber and plastic behavior and displays a clear rubber plateau between 0 and 50 degrees C with little temperature dependence. The apparent activation energy of flow for the latter material, determined by multifrequency DMTA, is 135 kJ mol(-1).