Preparation of All Polyester‐Based Semi‐IPN Elastomers Containing Self‐Associative or Non‐Associative Guest Chains via Post‐Blending Cross‐Linking

Mechanical properties of semi‐interpenetrating polymer network (semi‐IPN) elastomers consisting of chemical networks and self‐associative/non‐associative guest chains are demonstrated. Amorphous low T_g polyesters with thiol side groups (PE‐SH) are first synthesized by melt polycondensation. PE‐SH are then converted to polyesters containing COOH side groups (PE‐COOH) and amide side groups (PE‐amide) through Michael addition reaction of thiol groups with acrylic acid and acrylamide, respectively. Homogeneous semi‐IPN elastomers are obtained by thermal cross‐linking for bulk mixtures of PE‐COOH and PE‐amide in the presence of diepoxy cross‐linkers, where COOH and epoxy groups are reacted to form chemical cross‐links while the amide units form self‐complementary hydrogen bonds. Another sample containing non‐associative chains is also prepared by using polyester with N,N‐dimethylamide units, instead of PE‐amide. Dynamic mechanical analysis reveals that guest chain incorporation systematically brings plateau modulus reduction and a unique relaxation with higher tan δ value depending on the fraction and nature of guest chains. Tensile properties are also affected by the fraction and nature of guest chains; the incorporation of hydrogen bonded chains are beneficial to enhance breaking elongation and toughness without the sacrifice of maximum stress. The knowledge found in this work will be thus beneficial for creating tough soft materials with damping applications.