Synthesis and characterization of novel side-chain liquid crystalline polycarbonates, 5. Mesophase characterization of side-chain liquid crystalline polycarbonates with tails of different lengths

Abstract

SUMMARY:The mesomorphic properties and thermal stability of side-chain LC polycarbonates with alkoxyphenyl benzoate side groups having a short spacer and alkoxy tails ranging from 1 to 8 carbon atoms were studied by DSC, X-ray diffraction and polarized light optical microscopy. All polymers have a smectic A structure. Mesogens having short tails organize preferably in a monolayer structure, and mesogens having long tails in a double layer structure. A sharp increase in the clearing temperatures and enthalpies as a function of tail length was observed. No clear relation between the tail length and the glass transition temperature was found. Both the T g and the clearing temperature show a strong dependence on the molecular weight. Up to about M -w = 20 000 a rapid increase in phase transition temperatures with increasing molecular weight was observed, eventually levelling off to a constant maximum value. The LC polycarbonates were found to be thermally stable up to about 200 8C. At higher temperatures, random chain scission, resulting in a rapid decrease in molecular weight, and unzipping, resulting in the formation of a five-membered cyclic carbonate, are the main initial degradation mechanisms. The degraded polymers have lower transition temperatures than the original ones.

Photoresponsive side-chain liquid crystalline polymers with amide group-substituted azobenzene mesogens: effects of hydrogen bonding, flexible spacers, and terminal tails

“…As shown in Table 1, the phase transition temperatures of the azo polymers (i.e., the clearing points T cl ) increased markedly when the number of carbon (i.e., n) in the terminal alkyl chain increased from 4 to 12, but they levelled off when n was further increased. The groups of Jansen 46 and Picken 49 also found that the phase transition temperatures increased with increasing the tail length for a series of side-chain liquid crystalline polycarbonates and polyethers, respectively. In particular, it is noteworthy that the increase in the tail length led to a broader range of liquid crystalline phase (i.e., T cl -T g ) for P6/n, which is positive for potential applications.…”

“…In addition, a glass transition at 141, 144, 141, 129, 117 C was observed for P6/4, P6/6, P6/8, P6/ 12, and P6/18 in their DSC second heating scan, respectively, revealing that the glass transition temperatures (T g ) of the polymers at first slightly increased with an increase in the length of the terminal alkyl chains from n ¼ 4 to 6 and then decreased with a further increase in the terminal tail length, just as reported previously by others. 46 This phenomenon could be ascribed to the combined effects of the steric hindrance and plasticization function of the terminal alkyl chains on the T g of the polymers. While the steric hindrance effect might be dominant for the polymers with shorter terminal alkyl chains, the plasticization effect might play a more important role for those with longer terminal tails.…”

Functional Polycarbonates from Carbon Dioxide and Tailored Epoxide Monomers: Degradable Materials and Their Application Potential

“…Polycarbonates of this type have been prepared by several groups using glycidyl ethers containing mesogenic groups (Figure ; 22 , 23 ). Jansen et al synthesized side‐chain liquid crystalline polycarbonates with alkoxyphenylbenzoate side groups having a short spacer and tails ranging from 1 to 8 C‐atoms . The materials were prepared by an organo‐zinc catalyzed copolymerization of CO 2 and mesogenic 4‐alkoxyphenyl 4‐(2,3‐epoxypropoxy)benzoates, and all samples showed smectic A structures.…”

Fully renewable limonene‐derived polycarbonate as a high‐performance alkyd resin

“…On the other hand, the selective polymerization of functional epoxides, namely epoxy monomers with an extra functionality like an alkenyl, carbonate or hydrophilic group, receives wide attention because the corresponding functional polymers show interesting properties in many applications such as reactive substrates, coating resins and polymeric nanoparticles. [10][11][12][13][14][15][16][17] Recently, we have reported the chemo-selective alternating copolymerization of limonene dioxide and CO 2 , 18 leading to a new highly epoxy-functional linear aliphatic epoxy polycarbonate, poly(limonene-8,9-oxide carbonate) (PLOC; carrying a pendent epoxide group in every repeat unit), which can be an interesting polymer precursor for many applications, such as a degradable polymer backbone for alkyd resins (ARs). 19 Solvent-based alkyd paints typically consist of components such as solvents, binders, pigments, extenders and additives.…”