Chemical recycling to monomer (CRM) is a promising route for transitioning to a circular polymer economy. To develop new CRM systems with useful properties, it is important to understand the effects of monomer structure on polymerization/depolymerization behavior. In earlier work, this group demonstrated chemically recyclable polymers prepared by ring‐opening metathesis polymerization of
- Award ID(s):
- 1719875
- NSF-PAR ID:
- 10325430
- Date Published:
- Journal Name:
- Science
- Volume:
- 373
- Issue:
- 6556
- ISSN:
- 0036-8075
- Page Range / eLocation ID:
- 783 to 789
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract trans ‐cyclobutane fused cyclooctenes (t CBCO). Here, it is investigated how different substituents on cyclobutane impact the thermodynamics and thermal properties oft CBCO polymers. Introducing additional substituents to acis ‐diester functionalizedt CBCO is found to favor the conversion of polymerization; increased polymerization conversion is also observed when thecis ‐diester is isomerized into itstrans counterpart. The effects of these structural features on the thermal properties are also studied. These findings can provide important insights into designing next‐generation CRM polymers. -
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Abstract Equilibrium ring opening metathesis polymerization of low strained cycloolefins is opportunistic for the development of novel materials capable of chemical recycling to monomer (CRM). However, many of the potential materials for CRM contain complex side chains complicating predictions of their ring strain energies (RSE). The effects of different conformational considerations on RSE predictions using density functional theory (DFT) are explored. New homodesmotic equations are investigated to capture changes in olefin conformation upon polymerization. The employment of
cis ‐2‐butene as a corrective factor with a 2,7‐nonadiene linear analog bearing onecis and onetrans olefin (H2cis) resulted in RSEs similar to previously reported ΔH p values. Different consideration of possible conformers aside from their lowest energy counterparts leads to a range of predicted RSE values. Similarly, the application of a Boltzmann distribution resulted in negligible differences in RSE. Therefore, RSE predictions using the lowest energy structures with H2ciscalculated at B3LYP/6‐31+G* in toluene is a sufficient approach for predicting RSE of monomers with multiple conformers. This method can be used to screen a monomer's potential for CRM to reduce the time, cost, waste, and effort necessary to research new materials towards a more circular polymer economy. -
null (Ed.)Fossil fuel refining produces over 70 Mt of excess sulfur annually from for which there is currently no practical use. Recently, methods to convert waste sulfur to recyclable and biodegradable polymers have been delineated. In this report, a commercial bisphenol A (BPA) derivative, 2,2′,5,5′-tetrabromo(bisphenol A) (Br4BPA), is explored as a potential organic monomer for copolymerization with elemental sulfur by RASP (radical-induced aryl halide-sulfur polymerization). Resultant copolymers, BASx (x = wt% sulfur in the monomer feed, screened for values of 80, 85, 90, and 95) were characterized by thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. Analysis of early stage reaction products and depolymerization products support proposed S–Caryl bond formation and regiochemistry, while fractionation of BASx reveals a sulfur rank of 3–6. Copolymers having less organic cross-linker (5 or 10 wt%) in the monomer feed were thermoplastics, whereas thermosets were accomplished when 15 or 20 wt% of organic cross-linker was used. The flexural strengths of the thermally processable samples (>3.4 MPa and >4.7 for BAS95 and BAS90, respectively) were quite high compared to those of familiar building materials such as portland cement (3.7 MPa). Furthermore, copolymer BAS90 proved quite resistant to degradation by oxidizing organic acid, maintaining its full flexural strength after soaking in 0.5 M H2SO4 for 24 h. BAS90 could also be remelted and recast into shapes over many cycles without any loss of mechanical strength. This study on the effect of monomer ratio on properties of materials prepared by RASP of small molecular aryl halides confirms that highly cross-linked materials with varying physical and mechanical properties can be accessed by this protocol. This work is also an important step towards potentially upcycling BPA from plastic degradation and sulfur from fossil fuel refining.more » « less
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1126/science.abh0626
