Star-like polymer click-functionalized with small capping molecules: an initial investigation into properties and improving solubility in liquid crystals

Abstract

A novel class of polymer, star-like poly(tert-butyl acrylate) (PtBA) capped with 4-isocyano-4′-(prop-2-yn-1-yloxy)biphenyl (CNBP), with a well-defined size was synthesized via atom transfer radical polymerization (ATRP) and click reaction (i.e., azide–alkyne cyclization). The star-like architecture was composed of 21 separate arms connected to a high-functionality β-cyclodextrin (β-CD) core. The inner star-like PtBA blocks were hydrolyzed into poly(acrylic acid) (PAA), yielding star-like CNBP-capped PAA (i.e., star-like PAA-CNBP). The starlike polymers were characterized by gel permeation chromatography (GPC) and dynamic light scattering (DLS) to confirm narrow size distribution, as well as being examined by proton nuclear magnetic resonance (¹H-NMR), Fourier transform infrared spectroscopy (FTIR), Raman, and atomic force microscopy (AFM) to verify successful attachment of the click-functionalized capping agent (i.e., CNBP) with structural similarity to low molar mass liquid crystal, 4-cyano-4′-pentylbiphenyl (5CB). Structure and phase behavior were evaluated by AFM and optical imaging. Star-like PAA-CNBP was found to possess improved solubility in a liquid crystal host and interesting surface structures.