Nanocomposites of Liquid Crystalline Polyhedral Oligomeric Silsesquioxane Particles and Liquid Crystalline Polymers
- PDF / 229,930 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 117 Downloads / 276 Views
L9.10.1
Nanocomposites of Liquid Crystalline Polyhedral Oligomeric Silsesquioxane Particles and Liquid Crystalline Polymers
Alline P. Somlai, Subramanian Iyer, and David A. Schiraldi Department of Macromolecular Science and Engineering, Case Western Reserve University Cleveland, Ohio, 44106-7202, USA
ABSTRACT A new liquid crystalline nanoparticle has been synthesized by the reaction of a cyanobiphenyl derivative with polyhedral oligomeric silsesquioxane (POSS®*). Two POSS nanoparticles, liquid crystalline POSS (LC POSS 3) and a non-LC isooctyl POSS (OPOSS), were then compounded at 2.5 wt % into thermotropic polyester liquid crystalline polymers (LCPs) poly(hexamethylene 4,4’-bibenzoate), poly(diethylene glycol 4,4’-bibenzoate) as well as a frustrated LCP 45:55 poly(ethylene terephthalate-co-4,4’-bibenzoate). These polymers are currently being studied for potential use in high performance fibers and high barrier packaging materials. A comprehensive study of LCP/LC POSS 3 nanocomposites will focus on any changes in the thermal and mechanical properties of the LCPs with increasing LC POSS 3 concentration. It will be determined how incorporation of LC POSS 3 affects the liquid crystalline phases of an amorphous and crystalline LCP. Of special interest is the incorporation of LC POSS 3 into a frustrated LCP. It is proposed that the LC POSS 3 might help to unfrustrate the LCP. INTRODUCTION Polymer composites have been an intense area of investigation. Since polymer composites have shown reinforcement at the molecular level, there is a fundamental interest to explore polymer and filler interactions at the interphase. Traditional composites are made with micronsized fillers. However when these micron-sized fillers are used in LCPs, the filler size results in disruption of the mesophase order thereby destroying liquid crystallinity. An example of this is microtalc incorporation into Vectra A® resin [1]. A promising alternative for making LCP composites is POSS*, polyhedral oligomeric silsesquioxanes, a well-defined structure at the nanometer scale. POSS can have one or more reactive functionalities for modification to enhance compatibility in a polymer matrix. Several examples of modified POSS via hydrosilylation reactions resulting in liquid crystalline POSS are in the literature [2-6]. The chief aim of this work is to incorporate liquid crystalline POSS (LC POSS 3) into LCPs and a frustrated LCP to determine if the LC POSS 3/polymer interactions result in property improvements beyond those obtained using non-LC reinforcing agents. Others have shown that POSS incorporation, as fillers or in the polymer backbone, improves thermal properties of polymers such as Tg, Heat Deflection Temperatures (HDT), thermal stability (TGA), and flammability [7-10].
L9.10.2
EXPERIMENTAL DETAILS Materials, Characterization, and Processing Conditions OctaSilane-POSS® or 1,3,5,7,9,11,13,15-Octakis(dimethylsilyloxy)pentacyclo[9.5.1.13,9.15,15 .117,13]octasiloxane was purchased from Hybrid Plastics. The remaining chemicals were purchased fro
Data Loading...
