Interplay Between Viscoelastic and Chemical Tunings in Fatty-Acid-Based Polyester Adhesives: Engineering Biomass toward Functionalized Step-Growth Polymers and Soft Networks

Abstract

This Article describes the synthesis and characterization of renewable self-adhesive coatings with tunable viscoelastic properties and equipped with well-defined amounts of carboxylic acid "sticker" groups with adhesion promoting characteristics. Hydroxyl-ended polyesters with various architectures (linear, branched) were synthesized by melt polycondensation of dimerized fatty acids and fatty diols and then cured with maleic anhydride-modified triglycerides (such as maleinized soybean oil) in the presence of the amidine catalyst 1,8-diazabicyclo[5.4.0]undec-7-ene. The curing reaction of alcoholysis has the dual effect of chain extending/cross-linking the base polymers via creation of polymeric half-esters linkages while introducing carboxylic acid functions within the gel structure. We demonstrated how the adhesion properties can be finely tuned from molecular design and formulation of the network precursors and how the rheology and functionality of the coatings influence the adhesive bond formation and development. These renewable polyester adhesives proved to be suitable materials for pressure-sensitive adhesives applications with respect to adhesion strength, viscoelasticity, and functionality. In addition, the environmental benefits of such materials are briefly discussed.

Pressure-Sensitive Adhesives Based on Epoxidized Soybean Oil and Dicarboxylic Acids

“…It has also been demonstrated that polyesters from dimer acid and diols after being cured with maleic-anhydride-modified plant oils or epoxidized plant oils exhibited PSA properties. 16,17 In our previous study, PSAs were successfully prepared from a mixture of epoxidized fatty acids (EFAs). 18 The mixture of EFAs was prepared from ESO via the selective hydrolysis of the ester groups in ESO.…”

Development and Characterization of Pressure-Sensitive Adhesives from Dimer Acid and Epoxides

“…In addition, the PSAs contained hydroxyl groups (-OH) and a small amount of unreacted -COOH groups. The -OH and -COOH groups could improve the wetting of the PSAs on various adherends such as paper, glass, and skin, thus facilitating the intimate contact between the PSAs and the adherends (11,(23)(24)(25). These functional groups in PSAs could also significantly improve the adhesive strength of the PSAs through formations of hydrogen bonds between the PSAs and adherends (23)(24)(25)(26).…”

“…These functional groups in PSAs could also significantly improve the adhesive strength of the PSAs through formations of hydrogen bonds between the PSAs and adherends (23)(24)(25)(26). The -OH and -COOH groups also allowed formations of hydrogen bonds among molecular chains and within the same molecular chain of the PSA, thus increasing the cohesive strength of the PSA (11,(23)(24)(25)(26).…”

“…At present, commercial PSAs are mainly derived from acrylate-based copolymers, styrene-based block copolymers, ethylene-vinyl acetate copolymers, natural rubber, and silicone-based polymers. In recent years, a lot of effort has been devoted to development of PSAs from bio-based polymers, especially those from vegetable oils (3)(4)(5)(6)(7)(8)(9)(10)(11).…”

“…Another type of PSAs was recently developed from epoxidized soybean oil and phosphoric acid (7)(8)(9). It has also been reported that PSAs can be developed from the curing of polyesters from the condensation of dimer acid (DA) and diols with epoxidized plant oils (10,11). PSAs can also be developed from the polymerization of an AB-monomer, epoxidized oleic acid (12,13).…”