Camphene as a Mild, Bio-Derived Porogen for Near-Ambient Processing and 3D Printing of Porous Thermoplastics

Jeffrey L. Self, Han Xiao, Matthew M. Hausladen, Rafael A. Bramanto, Saurabh Shenvi Usgaonkar, Christopher J. Ellison

Research output: Contribution to journalArticlepeer-review

Abstract

Porous structures are ubiquitous in nature due to their advantageous mechanical and transport properties. These structures have inspired various synthetic porous polymer technologies, including lightweight structural materials and membranes. While many manufacturing processes have been developed to generate porous thermoplastics, these usually include hazardous processes, such as high pressures and temperatures, or chemical components. Furthermore, few are compatible with additive manufacturing methods, such as 3D printing. Herein, we introduce bio-derived terpene camphene as a solvent and porogen for the freeze-casting of thermoplastic parts under mild conditions. Enabled by a low melting point (50 °C), camphene is used as a solvent for melt processing camphene-polymer solutions at moderate temperatures that later undergo room-temperature crystallization to template polymer-rich domains. Due to its high vapor pressure, camphene can be sublimed directly from these biphasic structures, resulting in an interconnected microporous polymer structure. Various polymers are demonstrated to be soluble in camphene, including polystyrene, an olefinic elastomer, a polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene elastomer, a cyclic olefin copolymer, and poly(ethyl methacrylate). Porous samples of each polymer were generated from camphene mixtures via compression molding, cooling, and subsequent vacuum annealing at room temperature to remove camphene. The porosity and pore structures were dependent on solution composition, including both the polymer type and polymer loading. Across the compositions investigated, porosity decreased monotonically from 93 to 65% with increasing polymer content. In the case of polystyrene, samples with pore diameters varying from ∼20 to <5 μm were generated. Rheological measurements were conducted on a series of polystyrene-camphene solutions to understand and optimize the formulation and conditions for direct ink write 3D printing. Porous parts with complex structures were successfully printed under mild conditions. These results underscore the advantages of camphene as a sustainable, nontoxic porogen and will inform future development of porous polymer systems derived from these methods.

Original languageEnglish (US)
Pages (from-to)49244-49253
Number of pages10
JournalACS Applied Materials and Interfaces
Volume14
Issue number43
DOIs
StatePublished - Nov 2 2022

Bibliographical note

Funding Information:
We would like to acknowledge partial financial support from the Zsolt Rumy Innovation Chair and the NSF (grant # EFMA-1830950). M.M.H. acknowledges partial support from a 3M Graduate Fellowship. S.S.U. acknowledges partial support through a fellowship awarded by the PPG Foundation.

Funding Information:
This work was financially supported by the Zsolt Rumy Innovation Chair. The authors thank Prof. Lorraine Francis for providing valuable feedback and allowing use of the lab space for the 3D printing. The authors also thank Dr. David Giles and Dr. Asheesh Shukla for their help with instrumentation. Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from the NSF through the MRSEC (award number: DMR-2011401) and the NNCI (award number: ECCS-2025124) programs.

Publisher Copyright:
© 2022 Authors. All rights reserved.

Keywords

  • 3D printing
  • freeze-casting
  • mesoporous
  • porous polymers
  • thermoplastics

PubMed: MeSH publication types

  • Journal Article

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