A bio-inspired self-healing polymer system for sustainable plastics

Michael L Johnston, Purdue University

Abstract

Studying how marine organisms make tough biologic materials that autonomously heal allows us to integrate this biological self-healing motif into synthetic biomimetic polymers. These types of polymers will be used to develop components with greater fatigue life and toughness, promoting greater resource sustainability by reducing plastic consumption. The amino acid 3,4-dihydroxyphenylalanine (DOPA) grants marine mussels the ability to strongly affix themselves to the rocks under water by forming strong reversible bonds with their environment. Poly[(3,4-dihydroxystyrene)-co-styrene)] (P[3,4-DHS-S]) is a synthetic polymer mimic of DOPA with chemical structure similar to polystyrene (PS) with a potential self-healing mechanism. This intrinsic self-healing mechanism works to toughen and reform bonds to inhibit or retard crack propagation without external stimuli and energy. This work investigates the critical stress intensity for propagating preexisting cracks induced by a Vickers indentation in P[3,4-DHS-S], and the effects that different cross-linking agents have on crack growth within the polymer matrix. A Life Cycle Assessment (LCA) is also performed to give component designers supplemental information needed to evaluate any differences between using P[3,4-DHS-S] as an alternative to PS in terms of environmental and economic sustainability. A systematic evaluation of P[3,4-DHS-S] with a DHS content of 0%, 3%, and 30% was evaluated with soluble and particulate crosslinking agents to provide the reversible bond pathway. It was found that hydrogen bonding network provided by the catechol groups in the P[3,4-DHS-S] matrix is the dominant factor in providing additional toughness as compared to the crosslinking agents. The additional toughness of P[3,4-DHS-S] can provide incentive for its use as a replacement of PS to make smaller and tougher components. The results of this study suggest a P[3,4-DHS-S] with 3% DHS component can be reduced in size by an estimated 38% without loss of mechanical performance when compared to one made with pure PS. However, a chemical impact assessment demonstrated an increase in environmental impact categories when compared to the production of PS alone. This negative effect will be reduced as the scale for production of P[3,4-DHS-S] is increased.^

Degree

Ph.D.

Advisors

John E. Blendell, Purdue University, Jonathan J. Wilker, Purdue University.

Subject Area

Polymer chemistry|Materials science

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