Synthesis and Estimation of Poly[γ-(4-alkoxyphenyl)-benzyl-L-glutamate]s

Abstract

ABSTRACT:The synthesis and thermal properties of new thermo tropic liquid crystalline (LC) poly[y-4-( 4' -alkoxyphenyl)benzyl-L-glutamate]s (8) are described. y-4-( 4' -Alkoxyphenyl)benzyl-Lglutamates (6a-f) are prepared by the addition of 4-alkoxy-4' -hydroxymethylbiphenyl (3a-f) to N-phthaloyl-L-glutamic anhydride (4), followed by removal of the N-protecting group. 8a-f are synthesized by the polymerization of y-4-(4' -alkoxyphenyl)benzyl-L-glutamate-N-carboxyanhydrides (7a-f), which are prepared by treatment of 6a-f with phosgene. Although 8a--c do not show transition peaks in DSC heating curves, 8d-f show two endothermic transition peaks. Viewing on the hot stage with a polarizing microscope suggests that the first transition is due to the transition from the crystalline state to the I st LC state and the second one is attributed to the transition from the I st LC state to the 2nd LC state. Therefore, the long alkyl segment with more than a certain carbon number as the side chain of 8 is essential for the appearance of thermo tropic LC state.KEY WORDS Polypeptide / Poly(y-benzyl-L-glutamate) / Thermotropic Liquid Crystalline Polymer / During the past years, numerous polymers have been reported to form thermotropic liquid crystalline (LC) states. These thermotropic LC polymers-can be classified structurally into three types. Two of these types are well-known as main-chain and side-chain thermotropic LC polymers. 1 In the former, the mesogenic groups form the backbones of molecular chains; whereas in the latter, the mesogenic segments link to a polymer backbone as pendants in side chains. A third type 2 is relatively new and represented by polymers forming mesogenic rods surrounded by long hydrocarbon side chains. The transition from crystal to LC for the third type polymer seems to occur by melting of long hydrocarbon chains on heating and subsequently acting as solvents in the similar manner to the lyotropic LC state. 3 Therefore, the structures of polymers of the third type are closely relating to those of lyotropic LC polymers. For example, cellulose derivatives by Tseng et al., 4 • 5 poly(yalkyl glutamate)s by Watanabe et al. 2 • 6 and poly(y-alkoxybenzyl-L-glutamate)s by us 3 • 7 are thought to be thermotropic LC polymers of the third type.In this paper, we report the sythesis and thermotropic LC behavior of new poly [y-(4-861

Hierarchical Control of Internal Superstructure, Diameter, and Stability of Supramolecular and Macromolecular Columns Generated from Tapered Monodendritic Building Blocks

“…TLC: R f = 0.28 (2:1 hexanes/ethyl acetate). DSC: first heating, k 1 90 (0.42), k 2 134 (13.7), i; second heating, k 1 90 (0.47), k 2 134 (12.8), i; cooling, i 127 (13.6), k 2 (0.41), k 1 (lit . Mp: 134−135 °C).…”