Design of Mechanically Robust High-Tg Polymers: Physical Properties of Glassy Poly(ester carbonate)s with Cyclohexylene Rings in the Backbone

The incorporation of trans -cyclohexylene (C-ring) groups into the main chains of glassy polymers increases polymer chain dynamics. With the increase in trans-C-ring content in the main chain, both the coefficient of thermal expansion (CTE) of bulk specimens and the CTE of nanosized holes in these glasses increase. Trans-C-ring incorporation also increases T g and improves chain packing. These multiple effects are proposed to be due to ring inversion and the shape of the trans-C-rings: The ring inversion introduces enhanced local chain motion, which is proposed to reduce interchain interaction by decreasing the contact area and contact frequency between polymer chains. The trans configuration of C-rings has the effect of extending the polymer chains, which results in increased persistence length and improved chain packing. The increased persistence length leads to increased T g, even though the decreased interchain interactions would have the opposite effect. Substituting some trans-C-rings by cis-C-rings results in marked decrease in persistence length and therefore a significant decrease in T g . This further points to a correlation between persistence length and T g .