Stress-Strain and Stress-Relaxation Behaviors of Solution-Coated Layers Composed of Block Copolymers Mixed with Tackifiers

Takahiro Doi; Hideaki Takagi; Nobutaka Shimizu; Noriyuki Igarashi; Shinichi Sakurai

doi:10.1021/acsomega.1c01367

Stress-Strain and Stress-Relaxation Behaviors of Solution-Coated Layers Composed of Block Copolymers Mixed with Tackifiers

ACS Omega. 2021 Jul 1;6(27):17299-17313. doi: 10.1021/acsomega.1c01367. eCollection 2021 Jul 13.

Authors

Takahiro Doi¹, Hideaki Takagi², Nobutaka Shimizu², Noriyuki Igarashi², Shinichi Sakurai^{3

4}

Affiliations

¹ Advanced and Applied Research Institute, Nichiban Co., Ltd., Nihongi-Shinmachi, Anjo, Aichi 446-8531, Japan.
² Photon Factory, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan.
³ Department of Biobased Materials Science, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan.
⁴ Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati, Kamrup, Assam 781-039, India.

Abstract

The relationship between the mechanical properties and the structure of block copolymers mixed with tackifiers whose relative solubility to the respective components of block copolymers differs was examined. Coated layers were prepared by solution coating using a block copolymer composed of polystyrene (PS) and polyisoprene (PI), which forms spherical microdomains of PS in the PI matrix, mixed with three types of tackifiers: aliphatic (C5) resin, aliphatic-aromatic (C5-C9) resin, and rosin ester (RE) resin. Furthermore, the correlation between the changes in the nanostructure and mechanical properties including the stress-relaxation behaviors was clarified by two-dimensional small-angle X-ray scattering measurement. The amount of the PI-bridge conformation in the case of C5 resin is the lowest, resulting in the lowest stress. On the contrary, the largest amount of RE resin was solubilized in the PS phase so that it can be considered that pulling out of the PS chains took place easily. We were able to explain the stress-relaxation behavior by fitting with the three-component exponent functions. The triple exponential decay functions indicate the hierarchy of the structures that are the origins of the ″fast mode″ relating to the local relaxation due to the rotation of the repeating unit of polymer chains; the ″intermediate mode″ of the disentanglement of the mid-PI chains; and the ″slow mode″ relating to, in this particular case, pulling out of the PS chains from the PS sphere.