Aligned nematic elastomer

Abstract

There is provided the use of an aligned nematic elastomer to form a material having auxetic properties wherein the aligned nematic material has a mechanical Fréedericksz transition. Also provided is a method of producing an aligned nematic elastomer for said use.

1 . A method of producing a material having auxetic properties, said method comprising the steps of:
 a) providing an aligned nematic elastomer; and   b) forming an aligned nematic material using the aligned nematic elastomer, wherein the aligned nematic material has a mechanical Fréedericksz transition, thereby producing a material having auxetic properties.   
     
     
         2 . The method according to  claim 1  wherein the auxetic properties enable the material to be used in a medical device or in a biomedical application. 
     
     
         3 . The method according to  claim 1  wherein the auxetic properties enable the material to be used in a piezoelectric sensor or actuator, or in a micro- or nano-mechanical or electromechanical device. 
     
     
         4 . The method according to  claim 1  wherein the auxetic properties enable the material to be used in composite materials as reinforcements, or in personal protection clothing. 
     
     
         5 . The method according to  claim 1  wherein the aligned nematic elastomer comprises a monodomain liquid crystal elastomer. 
     
     
         6 . The method according to  claim 5  wherein the monodomain liquid crystal elastomer comprises; a polymeric component; a liquid crystal mesogen component; and a cross-linker component, wherein the liquid crystal mesogen component is physically linked to the polymeric component. 
     
     
         7 . The method according to  claim 6  wherein the liquid crystal mesogen component comprises a liquid crystal core component selected from the group consisting of aromatic rings, aliphatic rings, poly aromatic rings, poly aliphatic rings, phenyls, biphenyls, benzenes, and combinations thereof. 
     
     
         8 . The method according to  claim 7  wherein the liquid crystal core component is selected from one or more of the following systems: 
       
         
           
           
               
               
           
         
       
       wherein R and R′ are independently selected from the group consisting of alkyl, alkoxy, halide, —NO 2  or —CN and wherein the alkyl and alkoxy groups may be bivalent when forming part of the linking group which connects the liquid crystal core component to the polymeric component; and X and Y are independently selected from the group consisting of —CH═CH—, —C≡—, —CH═N—, —N═N—, or —C(O)O—. 
     
     
         9 . The method according to  claim 6  wherein the polymeric component is formed from both mesogenic and non-mesogenic components. 
     
     
         10 . The method according to  claim 9  wherein the polymeric component comprises an acrylate polymer and the non-mesogenic component comprises 2-ethylhexyl acrylate. 
     
     
         11 . The method according to  claim 6  wherein the crosslinker component comprises a mesogenic component. 
     
     
         12 . The method according to  claim 9  wherein the mesogenic component is 6-(4-cyano-biphenyl-4′-yloxy)hexyl acrylate, the crosslinker component is 1,4-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene, and the non-mesogenic component is 2-ethylhexyl acrylate. 
     
     
         13 . A method of producing an aligned nematic elastomer, said method comprising the steps of:
 a) applying an aligning means to a substrate   b) applying liquid crystal elastomer components to the substrate and allowing them to form an aligned nematic phase   c) curing the liquid crystal elastomer components to form an aligned nematic elastomer.   
     
     
         14 . The method according to  claim 13  wherein the aligning means is an aligning force which is applied by brushing the substrate.