Date of Award

January 2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Qianli R. Chu

Abstract

Gemini monomer, a new monomeric class that consists of two monomeric units connected by a covalent linker, can offer a highly dense polymeric framework. Moreover, their ability to form twice the number of covalent bonds than the conventional monomer can afford polymers with high thermal and mechanical strength. The desired Gemini monomer, ethylene 1,2-bis (2,4-pentadienoate) (EBP), was synthesized in two steps. First, an acid precursor 2,4-pentadienoic acid was synthesized by the condensation of malonic acid and acrolein. Second, ethylene glycol was used to connect two 2,4-pentadienoic acid units to obtain the monomer. Later, EBP was polymerized in ambient and solvent-free conditions to yield poly[ethylene 1,2-bis(2,4-pentadienoate)] (PEBP). This polymer was found to be inert with most of the organic solvents (DMSO, DMF, etc.), and was thermally stable (T5% > 300 °C) and displayed high Young’s modulus of up to 10.9 GPa with the mechanical strength of 159MPa.

Semi-rigid, thermally stable, symmetrical aliphatic building blocks suitable for materials synthesis are uncommon. One such class of structures is cyclobutane-containing building blocks (CBs). They bridge the gap between their flexible aliphatic chain and rigid aromatic counterparts. The presence of one or more conformational strained four-membered aliphatic rings in CBs gives them a unique blend of rigidity and processability, making them viable in designing and synthesizing novel polymers, metal-organic material, etc. Herein, we report a novel strategy to synthesize a CB, trans-1,3-cyclobutane dimethanol (CBDO-1), a versatile building block that may also serve as a phenol-free BPA replacement. It was synthesized using a facile photoreaction and subsequent reduction. Specifically, an initial photodimerization of trans-cinnamic acid using 365 nm blacklight was carried out to form a trans-1,3-cyclobutane diacid, CBDA-1, which was then reduced with either NaBH4 in the presence of I2, or by catalytic hydrogenation using CuO-CrO3, to give the desired CBDO-1 in excellent yield. To highlight the potential application of this useful primary diol, CBDO-1 and various diacids were used to synthesize novel polyesters via conventional melt polymerization. The thermal properties of this new series of polyesters were studied, including the glass transition temperature, which ranged from 33 to 114 °C, and the decomposition temperature, which ranged from 381 to 424 °C. The ease of synthesis of this cyclobutane-containing CBDO-1 monomer, coupled with its desirable properties, will help develop alternatives for the widely used BPA, and lead to novel and useful materials that are not accessible employing thermal reactions alone.

A diamine functionalized CB such as trans-1,3-cyclobutane diamine (CBAM-1) was obtained by the solid-state photodimerization trans-nitrostyrene in the slurry state using brine as a medium for forming a suspension. The characterization of CBAM-1 was done using NMR, FT-IR spectroscopy. For the first time, its structure was also determined by using SC-XRD. It was reckoned that semi-rigid CBAM-1 has the right balance of rigidity and flexibility, which can be translated into polyamides with increased processability and desired Tg suitable for various applications. Polyamides were synthesized using CBAM-1 and diacids such as succinic acid and terephthalic acid. Spectroscopic techniques were employed to characterize the polyamides, and their thermal properties were studied.

A biomass-derived CB such as rctt-di-2-furanyl-1,2-cyclobutanedicarboxylic acid (CBDA-2) was used as a semi-rigid polytopic ligand to the synthesis of two different green metal-organic materials with Cu2+ and Co2+ as the metal centers via a solution method. Both the 2D coordination polymers have been characterized by X-ray crystal structure determination and FT-IR spectroscopy. Also, their thermal properties were studied by using TGA and DSC. During this thermal study, both materials showed visual thermochromic behavior.

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