Date of Award
Master of Science (MS)
Qianli R. Chu
In this study, supramolecular polymers from carbamates are studied. A number of three-fold symmetric carbamates have been synthesized, characterized and their self-assembly structure are studied. The lamellar structures are detected and compared by using their melting points, NMR and FT-IR spectroscopy, and single crystal X-ray diffraction. The hydrogen-bond networks of each compound in crystalline state are examined. A new hydrogen bonded network self-assembles under mild conditions from benzene-1,3,5-triyl tris(butyl carbamate) (2), benzene-1,3,5-triyl tris(pentyl carbamate) (3), benzene-1,3,5-triyl tris(hexyl carbamate) (4), and benzene-1,3,5-triyl tris(heptyl carbamate) (5). One of the carbonyl groups in the molecules 2-4 does not form a C=O⋯H–N hydrogen bond in the sheet-like structure. Three different types of hydrogen bonding sites are observed. Although the building blocks only differ in the number of carbons in their side chains, this 2D unsaturated hydrogen bonded network is different from the saturated one which is self-assembled from benzene-1,3,5-triyl tris(propyl carbamate) 1. For compounds 2-5, the odd-even effect is also observed in terms of melting point, as well as the dihedral angle between the aromatic core and the arm with an oversaturated hydrogen bond. The inverted carbamates 7-11 are also synthesized and studied. An organic gel is found in triheptyl Nʹ,Nʹʹ,Nʹʹʹ-benzene-1,3,5-tricarbamate 11 with a concentration of 20 g/L (2.6 Ã10-2 M) in n-dodecane.
A mirror-symmetric building block for linear polymer is designed. 3,4-Di(furan-2-yl)cyclobutane-1,2-dicarboxylic acid (12) is synthesized from 3-(2-furyl)acrylic acid (12ʹ) through a solid-state [2+2] photocycloaddition by UV-A irradiation in quantitative yield. This building block molecule is derived from furfural and malonic acid. Thus, a novel 100% bio-based monomer has been successfully synthesized. For the first time, the single crystal is obtained in MeOH/DCM at room temperature. The thermal stability and acidic resistance of the cyclobutane ring of this building block is tested by thermal gravimetric analysis (GTA) and acid treatment. As a proof-of-concept, the condensation of 12 and 1,5-pentanediol is evaluated in this study. MS and NMR spectra of the product prove the formation of the target polymer.
A series of cyclic C2-symmetric building blocks for double-stranded polymers are designed. Our goal is to synthesize a linear polymer with double-stranded chains. The two strands are anchored by a C-C single bond so that the width is only extended by one covalent bond while the strength of the chain is enhanced. To achieve this polymer, a three-step strategy has been designed. The first step is to synthesize a cyclic monomer with a C=C bond at each end of the molecule. The second step is to apply intermolecular interactions for self-assembling the monomer. When desirable crystalline packing is obtained, the third step is to generate cyclobutane rings between each neighboring C=C bond by solid-state [2+2] photocycloaddition to form the double-stranded polymer. A series of lactone monomers have been successfully synthesized and their structures are confirmed by NMR spectroscopy. (3Z,14Z)-1,6,12,17-tetraoxacyclodocosa-3,14-diene-2,5,13,16-tetraone (17) is synthesized from maleic anhydride and 1,5-pentanediol. Then isomerization of compound 17 afford (3E,14E)-1,6,12,17-tetraoxacyclodocosa-3,14-diene-2,5,13,16-tetraone (18). Crystalline structures of these two compounds are analyzed by SCXRD and their photoreactivity is examined. The photopolymerization of 17 is supported by IR and solid state 13C NMR spectra.
Wang, Zijun Dave, "Synthesis And Applications Of Symmetric Building Blocks In Supramolecular, Single-Stranded, And Double-Stranded Polymers" (2016). Theses and Dissertations. 2085.