Copolymers with two different mesogens

Structural complexity abounds with this design since any two mesogens can, in principle, be combined and the two mesogens can be associated with different spacers and/or tail groups. There can, accordingly, be an 

A series of elegant studies by Percec et al has demonstrated some subtle, but significant, effects in copolymers based upon constitutional isomer pairs in methacrylate, acrylate and siloxane materials. The acrylic copolymers tended to be non-crystalline but the more flexible siloxanes were all crystalline, whatever the spacer length (Fig. 7.16, x O, y O, n 3). Controlled synthesis provided three series of materials (n = 3, 6 and 11) each including both homopolymers (x = 0, y= 100 and x= 100, y = 0 ) and copolymers of known composition. Each series provided its own information as follows. 

The n = 3 series was nematic and demonstrated that copolymerization depressed both K-N and N-i transition temperatures to similar extents (little effect on the overall persistence of the mesophase). However, the n = 11 series was smectic (as expected for long spacers) and exhibited a dramatic improvement in stability of the smectic phase. The S-i temperatures were little changed from the homopolymer values (411 K and 416 K for x = 0 and y = 0, respectively), while the K-S temperatures were greatly depressed (400 K for x = 0 and for y=0, but about 360 K for x=y = 50). The n = 6 series was (like n = 3) nematic, but (like n=ll) demonstrated 

---