Acrylic Triblock Copolymers Incorporating Isosorbide for Pressure Sensitive Adhesives

A new monomer acetylated acrylic isosorbide (AAI) was prepared in two steps using common reagents without the need for column chromatography. Free radical polymerization of AAI afforded poly(acetylated acrylic isosorbide) (PAAI), which exhibited a glass transition temperature (T_g) = 95 °C and good thermal stability (T_d, 5% weight loss; N₂ = 331 °C, air = 291 °C). A series of ABA triblock copolymers with either poly(n-butyl acrylate) (PnBA) or poly(2-ethylhexyl acrylate) (PEHA) as the low T_g midblocks and PAAI as the high T_g end blocks were prepared using Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization. The triblock copolymers ranging from 8-24 wt % PAAI were evaluated as pressure sensitive adhesives by 180° peel, loop tack, and static shear testing. While the PAAI-PEHA-PAAI series exhibited poor adhesive qualities, the PAAI-PnBA-PAAI series of triblock copolymers demonstrated peel forces up to 2.9 N cm^-1, tack forces up to 3.2 N cm^-1, and no shear failure up to 10 000 min. Dynamic mechanical analysis indicated that PAAI-PEHA-PAAI lacked the dissipative qualities needed to form an adhesive bond with the substrate, while the PAAI-PnBA-PAAI series exhibited a dynamic mechanical response consistent with related high performing PSAs.