Transformation of a kinetically prohibited mesophase of a linear polymer into an enantiotropic mesophase via cyclization

Abstract

MATERIALS(0.29g, estimated 0.96mmol of Br based on the molecular formula [C,,H,,Br].), copper(]) iodide (0.04 mmol, 4.0 mol.-%), and dichlorobis-(triphenylphosphine)palladium(n) or tetrakis(triphenylphosphine)palladium(o) (0.05 mmol, 4.8 mol.-%) in THF (3 ml) was added at room temperature a terminal acetylene (2.9 mmol, 3.5 eq) and diisopropykdmine (2.9 mmol, 3.5 eq). The black reaction solution was stirred at room temperature for 1 h then warmed to 60 "C for 10 h and 100 "C for 5 h. The reaction mixture was allowed to cool to room temperature and poured into water (20 ml). The organic layer was separated and the aqueous portion extracted with dichloromethane (3 x ) . The combined organic layers were washed with aqueous ammonium chloride (3 x). Filtration and removal of the solvent in vacuo gave a brown oil which was usually stirred with ether and the ether-insoluble solid was removed by filtration. No attempt was made to recover the catalyst, although the palladium catalyst would be soluble in the ether layer.

Self‐Assembled Shape‐Memory Fibers of Triblock Liquid‐Crystal Polymers

“…We synthesized a new triblock copolymer with a large central block composed of the main-chain nematic polymer [10] that has been extensively used in studies of nematic elastomers and demonstrated very large shape-memory effect. [4,11] The large shape change in the main-chain polymer is due to the highly anisotropic conformation it acquires in the nematic phase, with the chain folded into hairpins.…”

“…The startingmaterial1-(4-hydroxy-4′-biphenyl)-2-(4-hydroxyphenyl)butane, 1, was synthesized following the procedures of Percec and Kawasumi [10]. The a-(4-{1-[4′-(11-hydroxy undecanoxy)-biphenyl-4-ylmethyl]propyl}phenyl)-x- (11-hydroxy undecanoxy) poly[oxydecamethyleneoxy-4,4′-biphenyl-(2-ethylethylene-1,4-phenyl), (MCDIOL), was prepared using a modification of Finkelmann process [10,14], see Scheme 1.…”

“…The a-(4-{1-[4′-(11-hydroxy undecanoxy)-biphenyl-4-ylmethyl]propyl}phenyl)-x- (11-hydroxy undecanoxy) poly[oxydecamethyleneoxy-4,4′-biphenyl-(2-ethylethylene-1,4-phenyl), (MCDIOL), was prepared using a modification of Finkelmann process [10,14], see Scheme 1. Compound 1 was alkylated in absolute ethanol (EtOH) overnight with 10-bromoundecane-1-ol (2) under reflux conditions.…”

Distinct topography of erosion and new bone formation in achilles tendon enthesitis: Implications for understanding the link between inflammation and bone formation in spondylarthritis

“…The bulk of cyclic polymers studied by numerous research groups57–59, 62–66, 73, 74, 89, 95, 253, 268–289 comprised glass transition temperatures ( T g s), melting temperatures ( T m s), morphologies, melt viscosities, thermostabilities, and compatibilities. Cyclic PS, cyclic PEOs, and cyclic polysiloxanes were again the most widely studied cyclic polymers.…”

Cyclic polymers: Synthetic strategies and physical properties

“…[281][282][283][284][285][286][287] These cyclic oligoethers were prepared by phase-transfer-catalyzed polycondensations of a mesogenic but flexible diphenol with a,x-dibromoalkanes at low monomer concentration. Monodispers cyclic oligomers were isolated, and the influence of spacerlength and ring size on the temperature range of the nematic phase was studied.…”