Structural Development and Adhesion of Acrylic ABA Triblock Copolymer Gels

Abstract

Relationships between the structure, properties, and processing techniques of model polymer gels are investigated. The mechanical properties of the gels are determined by a thermally reversible aggregation of the syndiotactic PMMA end blocks of an acrylic triblock copolymer, which is diluted with a selective solvent for the center block. The adhesive and mechanical properties of these gels are related to their structural features, which are quantified by small-angle X-ray scattering experiments. The gels are significantly strengthened by the addition of low molecular weight isotactic PMMA homopolymers. These polymers form complexes with the syndiotactic PMMA end blocks of the triblock copolymer. In addition, we employ an axisymmetric adhesion test to demonstrate that the equilibrium gelation process can be utilized to reproducibly control the structure and adhesive properties of “dried” polymers. Acrylic acid moieties increase the adhesive performance of these materials without affecting their structure. By employing a unique gel casting process, a network structure with the desired properties can be formed, giving materials that are ideally suited for use as pressure-sensitive adhesives.

Tough Physical Double‐Network Hydrogels Based on Amphiphilic Triblock Copolymers

“…[ 19 ] Some studies of triblock copolymer gels in a mid-block selective solvent have revealed disordered structures of spherical domains of end-blocks, and the SAXS profi les of the gels were well fi tted by the Percus-Yevick hard sphere model. [ 20,21 ] The SAXS profi le in our study was also fi tted by the Percus-Yevick hard sphere model, and it well describes the peak positions when taking into consideration a Gaussian distribution of domain sizes ( Figure S2, Supporting Information). Thus, we consider that the hydrophobic blocks associate into randomly distributed, spherical domains, and these domains serve as the cross-links in the B gel.…”

Self-Assembly and Adhesion of DOPA-Modified Methacrylic Triblock Hydrogels

“…The water-soluble midblocks (PMAA) formed bridges between these domains, as was demonstrated previously for thermoreversible gels formed from similar triblock copolymers. 24,25 After solvent exchange, the hydrogels were immersed in water or controlled pH buffers, to study their equilibrium swelling properties in detail. The buffers were made by mixing equal volumes of 0.1 M Tris and HEPES solutions and adjusting the pH by the addition of 1 M sodium hydroxide.…”

Deformation and failure modes of adhesively bonded elastic layers

“…42 With this method, a 5 vol % polymer solution is made by dissolving the polymer in warm 2-ethylhexanol ͑TϾ70°C). The solution is then cooled to room temperature.…”

“…During the cooling process, the PMMA end blocks aggregate to form a physically crosslinked gel. 42 A small quantity of the gel is molded onto a glass slide to give a layer of known thickness. This gel layer is then dried at room temperature for several days until all of the solvent is removed.…”

“…Details of the gel microstructure, the effects of drying, and the advantages of gel casting over solution casting have been given by Flanigan, Crosby, and Shull. 42 The PEHA samples were prepared by depositing a small quantity of latex onto a glass slide and doctor blading the quantity of sample to achieve a uniform film. This latex layer is then dried at room temperature and annealed for 4 h at 70°C under vacuum.…”