Synthesis And Properties Of New Liquid Crystalline Monomers And Cholesteric Elastomers

Besides the optical and orientation property of the liquid crystal,the liquid crystal elastomer also has excellent mechanical property and chemical stability of the network polymer. It has became an hot topic during the liquid crystal polymer research area. Therefore, study on cholesteric LCEs holds not only important theoretical purpose, but also potential applications in numerous areas, especially in the fields of piezoelectric materials and nonlinear optics etc.In this dissertation, five chiral monomers (M1-M5) and two LC crosslinking agents (M6, M7) were synthesized, which include 4-(menthyloxyacetoxyl)phenyl-4'-(2-allyloxy-benzoyloxyethoxy)benzoate (M1),4-(menthyloxyacetoxyl)biphenyl-4'-(2-allyloxybenzoyloxy-ethoxy)benzoate (M2),4-(menthyloxyacetoxylbenzoyloxy)phenyl-4'-(2-allyloxybenzoyloxy-ethoxy)benzoate (M3),4-(menthyloxyacetoxyl)biphenyl-4'-(6-allyloxybenzoyloxyhexyloxy) benzoate (M4),4-(menthyloxyacetoxylbenzoyloxy)phenyl-4'-(6-allyloxybenzoyloxyhexyloxy) benzoate (M5),4-(10-undecylen-l-yloxy)biphenyl-4'-allyloxybenzoate (M6) and 4-(10-undecylen-1-yloxy)phenyl-4'-allyloxybenzoate (M7). In addition,we synthesized M2～Ms with PMHS to obtain four homopolymers(PM2-PM5),respectively. And synthesizing M2 and M6,M4 and M7 to obtained two series of liquid crystal elastomers accordingly.Furthermore, all the polymers are liquid crystal polymer. Both the monomers and crosslinking agents and polymers never be seen in or outside the nation..In the dissertation,the structures and properties of the obtained LC monomers, crosslinking agent, LCEs were investigated by FT-IR spectroscopy,1H-NMR spectroscopy, polarizing optical microscopy (POM),thermogravimetric analyses (TGA), and differential scanning calorimetry (DSC). Moreover,the relationship between the structure of monomers and the crosslinking agents and the liquid crystal properties. Furthermore,the effects of crosslinking agents content on the phase behavior were also investigated. All the monomers and crosslinking agents are liquid crystals except the M1. M2-M5displayed enantiotropic cholesteric phase, and exhibited oily-streak texture and finger print texture on heating process and focal-conic texture on cooling cycle, and the melting temperatures (Tm) and clearing or isoropic temperatures (Ti) decreased with increasing flexibility chain segments. There are typical nematic texture of schlieren both in the heating or cooling measurement of crosslinking agents M6 and,while M6 also appeared fan-shaped texture of smectic A(SA) during heating period and appeared fan-shaped texture of smectic SA,cracked fan-shaped texture of smectic C(SC) and mosaic texture of smectic B(SB).All the homopolymers (PM2～PM5) presented Grandjean texture,and the glass temperature Tg decreased with increasing of the flexibility chain segments.Both the two series of the elastomers appeared Grandjean texture too.When refer to the two seties elastomers, Our research focus on the effects that causing by different contents of crosslinking agents on the phase behavior and thermodynamic properties of elastomers.With the increasing of the contents of crosslinking agents, Tg decreased at first and then. Increased,this is due to two aspect effects(cross linkung and plasticizing)that crosslinking agents have on the LCEs. When the degree of cross linking is not big enough, the plasticizing effects contributes more to the effects,as a result the Tg of LCEs is lower than that of the Tg of according polymer without crosslinking agents.With the increasing of the crosslinking agents,the cross linking becomes the main effects,the Tg of LCEs is bigger than the Tg of according homopolymer at this time,and the Ti of elastomer PM2 increased at first and then decreased when the content of crosslinking agent is 12mol%.Furthermore,according to the result ot TGA,the decomposed temperature of the elastomers are higher than 330.0℃,it means they all have excellent stability.