Improved properties, performance and recyclability of thermoset polymers and composites processed by frontal ring-opening metathesis polymerization (FROMP)

Ivanoff, Douglas George

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Description

Title

Improved properties, performance and recyclability of thermoset polymers and composites processed by frontal ring-opening metathesis polymerization (FROMP)

Author(s)

Ivanoff, Douglas George

Issue Date

2021-10-11

Director of Research (if dissertation) or Advisor (if thesis)

Sottos, Nancy R

Doctoral Committee Chair(s)

Sottos, Nancy R

Committee Member(s)

• Moore, Jeffrey S
• Evans, Christopher M
• Schweizer, Kenneth S

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• frontal polymerization
• glass transition temperature

Abstract

Frontal polymerization (FP) allows for a reduction in both energy and time required for production of polymeric materials by utilizing the large exothermic heat of polymerization to cure the material. The research described in this thesis explores and quantifies the effect of cure method on the thermomechanical behavior of composites and polymers while addressing the need for new FP monomers that allow for new functionalities, such as heat-resistance and recyclability. Frontal ring-opening metathesis polymerization (FROMP) of dicyclopentadiene (DCPD) has been demonstrated for the fabrication of neat polymers and fiber reinforced polymer composites (FRPC). Comparison of FRPCs with an epoxy matrix and pDCPD matrix reveals a weak interface between pDCPD and carbon fiber, reducing the mechanical properties. The limitation in interface strength is addressed in traditionally cured pDCPD by including adhesion promoters in the DCPD to react with the surface functionality of the carbon fibers. Structural components require high stiffness at elevated temperatures, necessitating high-glass transition temperature (Tg) polymers. The FROMP of DCPD resultants in thermosets with a Tg of ~130 °C, restricting use to low-temperature applications. The limitation on the maximum operating temperature of pDCPD is addressed by synthesizing norbornene-based crosslinking co-monomers. Frontally polymerizing crosslinking co-monomers with DCPD reduces the molecular weight between crosslinks (Mc), resulting in a polymer with a significantly higher Tg ( > 215 °C). Many thermosets have been designed without an end-of-life strategy and are inherently difficult to recycle into useful compounds. The incorporation of cyclic olefins featuring acetal or silyl ether linkages into DCPD allows for FROMP of pDCPD thermosets that fully deconstruct into oligomers with hydroxyl functionality. The material is upcycled by combining the deconstruction fragments with a diisocyanate to form a new polyurethane network with a Tg of 155 °C. The thermomechanical limitations imparted by the comonomers are overcome by synthesizing difunctional crosslinkers connected via a deconstructable silyl ether linkage. Development of new FROMP monomers enables control over reaction kinetics and thermodynamics, crosslinking density, and chemical stability of the resultant polymers. The research improves the library of FROMP monomers in two major categories: multifunctional crosslinking and degradable/recyclable. The first class is approached by synthesizing compounds featuring norbornene moieties, and recyclability is achieved via incorporation of dynamic silyl ether and acetal bonds in the polymer backbone and between crosslinks.

Graduation Semester

2021-12

Type of Resource

Thesis

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Copyright 2021 Douglas Ivanoff

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