Supramolecular mainchain liquid crystalline polymers and networks with

Supramolecular main-chain liquid crystalline polymers and networks with competitive hydrogen bonding: a study of rigid networking agents in systems with competitive hydrogen bonding Dustin D. Fredrickson, Alexander E. Waner, Kurt N. Wiegel Research: Careening from catastrophe to catastrophe since 2000 Department of Chemistry, University of Wisconsin, Eau Claire WI 54702 Background Liquid Crystals • Materials that exhibit long-range and some short-range directional ordering in a fluid state. • Composed of mesogens (shaped molecules) and flexible spacers • Different types of mesogens based on molecular shape (calamitic: rodshaped) Molecular Self-assembly Through Hydrogen Bonding Non-covalent interactions formed between two molecules through a hydrogen -bond resulting in a larger “associated” molecule Mesogenic Networks • Combine characteristic of networks and liquid crystals • Couple physical deformations with liquid crystalline phase behavior • Thermoreversability through hydrogen bonding would introduce lability and the ability to reorganize to these characteristics Materials Used Thermal Analysis • • • Complexes synthesized through standard melt-complex methodology DSC data determined on a Mettler-Toledo STAR e 1 DSC at 10°C/Min heating rate unless otherwise noted Optical micrographs were measured using a Mettler-Toledo FP 82 Hotstage Mounted on an Olympus BHT polarizing light microscope at a 10°C/Min heating rate unless otherwise noted 4 EOBBA/2 RP/n. SBZ Networks % 4 SBZ 0 5 10 15 20 25 30 35 40 45 50 55 60 62. 5 65 100 KI 172. 45 X X 170. 1 169. 5 169. 4 166. 2 166. 5 164. 5 162 161. 5 169. 2 159. 8 153. 2 143. 3 153. 5 % 3 SBZ 0 5 10 15 20 25 30 35 40 45 50 55 57. 5 60 70 90 100 %2 Sb. Z Synthetic Methodologies Optical Images KI 172. 45 171. 33 171. 86 171. 66 167. 63 167. 15 166. 73 167. 29 163. 35 161. 3 162. 85 159. 42 159. 05 150. 4 164. 13 165. 45 164. 99 KI 0 5 10 15 20 30 40 45 50 57. 5 60 65 70 100 KN X 118. 2 119. 9 X X X X NI X 170. 5 167. 8 X X X X IN 173. 47 170. 92 169. 97 167. 31 159. 47 160. 04 158. 01 159. 61 151. 24 145. 59 146. 07 144. 74 X X X IN 172. 45 173. 71 172. 1 169. 85 169. 31 168. 05 163. 69 153. 92 153. 82 155. 4 154. 59 155. 04 151. 54 165. 28 IN 173. 17 171. 4 161. 1 165. 1 163. 5 161. 3 156. 4 154. 7 152. 6 146. 5 147. 9 139. 3 143. 5 141. 6 X X NS 165. 31 160. 62 X X X X NS 174. 43 175. 83 171. 44 168. 34 166. 48 161. 59 154. 06 145. 39 144. 37 138. 36 X X NS 165. 31 160. 1 X X X X SK 148. 62 144. 49 X X X X SK 166. 67 166. 6 161. 17 155. 57 X X X X X SK 148. 62 144. 6 X X X X NK X X 146. 03 144. 6 134. 88 137. 15 134. 92 136. 4 128. 4 108. 68 130. 22 115. 5 X X X NK 152. 36 150 145. 87 141. 07 X X X X X NK X X 139. 9 141. 2 140. 6 138. 0 133. 1 130. 9 123. 2 120. 1 117. 8 124. 9 Vit X X IK X X X X 135. 9 122. 7 KI X X X 138. 01 121. 06 135. 07 138. 35 131. 84 IK X X 139. 27 133. 72 122. 2 111. 54 111. 52 115. 37 X X X X 119. 76 118. 44 117. 63 142. 68 Results/Observations • The associative chain structures displayed mesogenic characteristics at loadings dependent on the functionality of the crosslinking agent • 4 SBZ • Complexes displayed enantiotropic mesogenic phases in loadings up to and including 10% • Smectic phases were observed in the cooling cycle up to the same concentrations. • Above 10%, only montropic (cooling) phases were observed up to 62. 5% inclusion. • 3 SBZ • Loadings of 3 SBZ displayed monotropic phases in concentrations up to 55% • Smectic phases observed up to 5% loading. • 2 SBZ • 2 SBZ as disrupting agent nematic in loadings up to 57. 5% (smectic phases observed up to 15%). Conclusions Supramolecular liquid crystalline networks and polymers have been synthesized with a flexible bisbenzoic acid group and two pyridyls: A small rigid bipyridyl capable of forming a mesophase A series of rigid poly-pyridyls that serve as liquid crystalline disruptors. It was found that the inclusion of the disruptor units varied according to the functionality. Tetra-functionalized species destroyed nematic phases at 62. 5%, Tri at 55% Bi at 57. 5% loadings. These inclusions concentrations are markedly higher than those seen in analogous onering poly-pyridyl networking agents. One supposition for this phenomenon is the increased rigidity of the n. SBZ series is less disruptive to the overall formation of a mesophase. Acknowledgements This work was funded by the Petroleum Research Foundation (54134 -B 7), National Science Foundation (Award Numbers 0804428 and 1105256) and UW-EC Office of Research and Sponsored Programs