A molecular design to enhance the ductility of high Tg glassy polyestercarbonates

Three series of polycarbonates, polyestercarbonates and polyesters based on 3,3,3′,3′-tetramethyl-1,1 ′-spirobi-indane (SBI), 4,4′-(3,3,5-trimethyleyclohexylidene)diphenol(Tmc) and 4,4′-cyclohexylidene diphenol (BPAZ) have been successfully designed and synthesized. Cyclohexylene groups (C-rings) were incorporated into the backbones of these polymers. Glassy amorphous polymers with T _g as high as 280°C and with good ductility were obtained.; The main chain C-rings were shown undergoing chair-chair conformational transition by dynamic mechanical analysis (DMA). The change in secondary relaxation strength of these polymers were shown to correlate with the total concentration of C-rings instead of only the main chain cyclohexylene groups.; The coefficients of thermal expansion (CTE) of both the bulk specimens and the nanosized holes (probed by positron annihilation lifetime spectroscopy) increase with increasing content of main chain C-rings, but there is no correlation between CTE values and the total concentration of C-rings. A linear correlation between the elastic modulus and the inverse of CTE exists after the secondary γ relaxation is complete. A near linear correlation between the modulus and the yield stress at room temperature also exists. Both modulus and yield stress decrease with increasing content of main chain C-rings. (not the total C-rings). These results indicate that elastic modulus and yield stress, like thermal expansion, are predominantly controlled by intermolecular forces. We propose that the main chain ring inversion of the cyclohexylene groups and the segmental motion enhanced by these ring inversions effectively modulate interchain interactions by decreasing the contact area and contact time of interacting chains, thus reducing the interchain forces.; The reduced tendency to necking in tensile tests of these polymers with increased content of main chain C-rings reflect the enhanced dynamics. The enhanced dynamics can effectively relax strain localization, thus reducing the tendency to necking. The enhanced dynamics is also reflected in the Eyring's flow volume.; Chain stiffness described by persistence length is the main factor in controlling T_g. Main chain trans C-rings can extend polymer chain, thus increasing its stiffness.