Preliminary Study On Concentrated Solution Properties Of Mesogen-jacketed Liquid Crystal Polymers

The Mesogen-jacketed liquid crystal polymers (MJLCPs) is a kind of semi-rigidchain polymer, in theory, it has formed lyotropic liquid crystal polymer. So people aredevoted to search suitable conditions, making mesogen-jacketed liquid crystalpolymers become lyotropic liquid crystalline. Unfortunately, they have failed to makeit. Herein we designed and synthesized a novel MJLCP, making it become lyotropicliquid crystaline in suitable conditions, which will be meaningful in academicresearch and practical applications.Two kinds of MJLCPs, poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrenes}PMPCS and poly{2,5-bis[(4-butyloxyphenyl)oxycarbonyl] styrenes}PBPCS,were successfully synthesized via free radical polymerization. The PMPCS is thetypical MJLCPs in which liquid crystalline phase doesn’t disappear whatever thetemperature change. The other is a re-entrant phase’ MJLCPs which liquid crystallinephase will disappear during cooling. Based on these two kinds of polymers, westudied the phase behavior of concentrated solution of MJLCPs through mixingdifferent small molecules. Compared with the phase behavior of homopolymers,polymer/small molecules blends have displayed the more interesting phase behavior.The main topics of paper are as follows.(1) Firstly, the molecular characterizations of the polymers were performed with~1H NMR and gel permeation chromatography (GPC). Secondly, different smallmolecules were successfully designed and synthesized, such as4-methoxyphenol,4-n-butoxyphenol,4-n-hexyloxyphenol. And the molecular characterizations of thesmall molecules were performed with1H NMR. Thirdly, the blend samples ofMJLCPs were prepared as follows. The weight polymers and small molecules weredissolved in THF, heating to70oC for2hours, quenched to room temperature, andrequisite amounts of the polymers and4-alkoxyphenol were dissolved in THF and thedried in vacauum. The compositions of the blends are expressed by mass percentageof polymers.(2) The phase behaviors of concentrated solution of the PMPCS wereinvestigated by a combination of techniques including differential scanningcalorimetry (DSC), polarized optical microscopy (POM). The experimental resultsshowed that the more longer the samll molecules has alkoxy tails, the more easier concentrated solution of polymer are to produce phase separation, lead to be appearedof the re-entrant phenomenon in the harsh conditions. When the PMPCS blends withsmall molecules, the glass transition temperature significantly reduced. Andconcentrated solution of polymer display the re-entrant phenomenon in mass fractionrange (74-83%),(80-87%),(82-87%), blending with small molecules with differentalkoxy tails1C,4C and6C, respectively. So the plasticization of small molecules hasplayed an important role in the phase behaviors of polymers.(3) The phase behaviors of concentrated solution of the PBPCS were investigated.The experimental results are similar with the PMPCS’.And concentrated solution ofpolymer display the re-entrant phenomenon in mass fraction range (65-100%),(66-100%),(80-100%). In addition, the liquid crystalline phase occurred in lowertemperature with the growth of the content of the small molecule.In summary, the small molecules have played an important role in the phasebehaviors and the re-entrant phenomenon of the corresponding polymers.