|dc.description.abstract||A series of nonpolar segmented polyurethaneurea(PUU) with bulky side group have been synthesized and their structure-property relationship have been investigated. The bulky group is a molecule that can make a space about 1nm beside the backbone to interfere the hard segment domain. The PUU based on 4,4’-dicyclohexylmethane diisocyanate (H12MDI), polyisoprene(Poly-IP,MW 2500),ethylenediamine(EDA) and two kinds of bulky groups are synthesized by two-step solution polymerization. Hard-segment content (35,45,55,70 wt%) and bulky group contents (0,4.5,8,10,15 wt%) are varied and their effect on the properties are studied. Properties are studied by Fourier-Transform Infrared(FT-IR),Differential Scanning Calorimetry(DSC),Dynamic Mechanical Analysis(DMA) and tensile-strain testing.
The bulky groups (I and II) are two kinds of self-synthesized amide-diol that are reacted by trimethylacetic acid(TMAA) and dipropylacetic acid (DPAA) separately with 2-Amino-2-methyl-1,3-propanediol(AMPD). Chemical structures of bulky groups are characterized by FT-IR, Nuclear Magnetic Resonance(NMR) and Mass Spectroscopy (MS).The yields of bulky I and II are about 42.5% and 40.7%.
The introduction of bulky group result in the C=O stretching of urea and urethane both shift to higher wavenumbers means that the hydrogen bonding strength is reduced. The storage modulus, Young’s modulus and tensile strength are increasing with increasing hard-segment content, but elongation at break is decreasing on the contrary. As the bulky group exists in PUU, the hard-segment domain may become loosely that is to say intermolecular force (cohesive energy) between hard segments is weakening. So the mechanical properties are reduced including Young’s modulus, tensile strength and elongation at break.||en_US|