The effect of terminal alkyl chains on hyperbranched polyesters based on 2,2-bis(hydroxymethyl)propionic acid

A hyperbranched hydroxyfunctional polyester based on 2,2-bis(hydroxymethyl)propionic acid as AB(2)-monomer and a tetrafunctional polyol as core was end-capped with five different alkylacyl chlorides. Alkyl chain lengths ranging from three to sixteen carbons were used. Short alkyl chains (3-6 carbons) decrease the glass transition temperature from around 30 degrees C for the hydroxyterminated polyester to temperatures well below zero. With a sufficiently long alkyl chain (12-16 carbons) the polymers tend to crystallize. The polyesters with C-16-chains as terminal groups exhibit several different crystalline phases as revealed by differential scanning calorimetry. From X-ray data it was possible to suggest that the crystallization for the C-16-terminated samples occurs in a non-interpenetrating fashion for the larger sample and in an interpenetrating way for the smaller polymers.