Date of Award
Doctor of Philosophy (PhD)
Qianli R. Chu
A series of sustainable polycyclobutane (PCB) materials were prepared from biomass-based chemicals by [2 + 2] photocycloaddition reaction in sunlight/floodlight or conventional organic synthesis. At the beginning, a family of gemini monomers was synthesized from furfural, which can be obtained from corncobs. First, a photoreactive building block, 3-(2-furyl)acrylic acid also called (E)-3-(furan-2-yl)acrylic acid, was synthesized from furfural and malonic acid. Five photostable diols were used to connect two photoreactive building blocks to obtain the monomers. These synthesized monomers were characterized by NMR, UV-Vis and FT-IR spectroscopy, XRD, P-XRD, TGA, and DSC. The photoreaction was monitored by FT-IR spectroscopy and the results indicated that all of the monomers were photoreactive. XRD analysis suggested that these monomers can be used to synthesize polyladderanes and linear polyesters. Monomer (2E,2'E)-butane-1,4-diyl bis[3-(furan-2-yl)acrylate] formed a polyladderane. Two pieces of independent evidence were obtained, single-crystal-to-single-crystal (SCSC) and a dimer intermediate. Monomer (2E,2'E)-pentane-1,5-diyl bis[3-(furan-2-yl)acrylate] formed a linear polyester thermoplastic. Both the polyladderane and linear polyesters are amorphous. TGA and DSC showed they decomposed around 300 oC.
Two-dimensional (2D) polymers were synthesized from cinnamic acid, which can be obtained from cinnamon and from a byproduct of biofuels manufacture. Four molecules of cinnamic acids were linked with a durene group through nuclear substitution reaction. This
four-armed monomer provided four reacting centers, which was the key forming a 2D polymer. The obtained 2D polymer was insoluble in most common organic solvents. The thin layered 2D polymer was observed under TEM and SEM after exfoliation in DMF and H2O. The key hydrolysis product trans-2,4-diphenylcyclobutane-1,3-dicarboxylic acid or alpha-truxillic acid was captured, which proved the newly formed cyclobutane rings.
The alpha-truxillic acid has two carboxylic groups on the opposite sides of the cyclobutane rings which, provided a semi-rigid structure. This diacid is one of the family members of cyclobutane-diacids (CBDA). This class of diacid can be used to synthesize thermoplastics through conventional synthetic method. Four polyesters, PEAT, PBAT, PPAT5 and PHAT, were successfully prepared from trans-2,4-diphenylcyclobutane-1,3-dicarboxylic acid (CBDA-1) by coupling reactions. TGA showed a high thermostability of these polymers. DSC results showed glass transition temperature decreased as the carbon chains increasing, which may be due to the flexibility of the polymers.
Wang, Zhihan, "Polycyclobutanes Constructed From Biomass-Based Building Blocks" (2017). Theses and Dissertations. 2153.