Polymers, liquid crystalline thermal characterization

As briefly mentioned earlier, thermal studies have been used in conjunction with characterization by polarized light microscopy to determine the miscibility of polymeric and small molecule liquid crystals and low molecular weight mesogens, of the same or different types of liquid crystallinity, can also be used as plasticizers or diluents for polymers, as demonstrated in a study involving side chain liquid crystalline polymers... 

Characterization. The liquid crystalline properties of the side-chain monomers (III) and polymers (I) have been studied by Differential Scanning Calorimetry (DSC), Polarized Optical Microscopy (POM) and X-ray diffraction. The thermal transition data and phase types for all monomers (III) and polymers (I) are summarized in Table HI. A representative DSC scan for the monomer (El) and polymer (p with a four-carbon tail (n=4) and six-carbon flexible spacer (m=6) are shown in Figures 1 and 2 respectively. The first peak at -24°C shown in Figure 1 is the crystal to smectic... 

The thermal reaction of cobalt polymers 4.28 with isocyanates at 120 °C leads to 2-pyridone-containing polymers such as 4.30 [70]. Well-characterized, yellow polyesters 4.31 containing skeletal (cyclobutadiene)cobalt moieties in the main chain have been prepared by interfacial polycondensation approaches [73]. The use of solubilizing alkoxy substituents R afforded materials with Mn = 5,400-16,300 (PDI = 1.3-1.8). Analogous materials to 4.31 with a 1,3-disposition of the main-chain substituents on the cyclobutadiene ligands have also been studied [73, 74]. Thermotropic liquid crystallinity was detected by polarizing microscopy, with, in some cases, mesophases stable over the temperature range from about 110 to >250°C. 

Ringsdorf and his group have reported the synthesis and thermal characterization of liquid crystalline polymers with methacrylate and acrylate backbones in which the mesogenic groups are in pendant side chains.2,9,11 Some of their results are shown in Figure 6. 

Malik TM, Carreau PJ, Qiapleau N (1989) Qiaracterization of liquid crystalline polyester polycarbonate blends. Polym Eng Sci 29(9) 600-608 Manson JAE, Seferis JC (1992) Process simulated laminate (PSL) a methodology to internal stress characterization in advanced composite materials. J Compos Mater 26(3) 405 31 Meng YZ, Tjong SC, Hay AS (1998) Morphology, rheological and thermal properties of the melt blends of poly (phthalazinone ether ketone sulfone) with liquid crystalline copolyester. Polymer 39(10) 1845-1850... 

In the present work, terephthalic acid was successfully regenerated from PET waste bottles via saponification process in high yield and purity. The new liquid crystalline poly(azomethine esters) based on terephthalic acid were prepared and characterized successfully using important and vital spectroscopic methods. The combining results that obtained from DSC, POM and XRD studies were confirmed the liquid crystallinity of the poly(azomethine esters). AU the polymers exhibit nematic mesophases except that for polymer 3(a). Furthermore, TGA results also confirmed that the new synthesized polymers possess high thermal stability. 

Li YZ, Badrinarayanan P, Kessler MR (2013) Liquid crystalline epoxy resin based on biphenyl mesogen thermal characterization. Polymer 54 3017-3025 Lin QH, Yee AF, Earls JD, Hefner RE, Sue HJ (1994) Phase-transformations of a liquid crystalline epoxy during curing. Polymer 35 2679-2682... 

On second heating the clearing point is observed at a slightly lower temperature this is apparently attributable to a slight decomposition and/or polymerization of the monomer. The liquid crystalline character of the monomer was also established by thermal analysis. As seen from DSC cooling traces, in Fig. 2, there is substantial supercooling of the mesomorphic phase. The polymer used for liquid crystalline characterization... 

Noncrystalline polymers are characterized by the absence of long-range order, other than that associated with prerequisite connectivity of the polymer molecule itself. However, to merely classify a polymeric material as "amorphous" serves only to both overlook the various substructures that may exist, and fail to account for the particular differences in macroscopic properties which result from varying chemical configurations, or from, for example, specific thermal or mechanical treatments. In terms of classification, the first order structures of "noncrystalline" polymers are clearly not crystalline or liquid crystalline, and we usually have an a priori knowledge of the chemical configuration. Rather, the interest in structure in noncrystalline polymers and its interaction with bulk properties is centered on additional somewhat subtle variations in molecular... 

The potential of vibrational spectroscopy for polymer characterization can be considerably enhanced if it is applied as time-resolved technique to polymers trader external perturbations or combined with other analytical techniques, thereby providing different types of physical data that have been simultaneously acquired on the same sample. In this respect, specifically the combination of vibrational spectroscopy with thermal or mechanical measurements has contributed toward a better understanding of the stmctural changes as a consequence of the external perturbation. Furthermore, FT-IR spectroscopic studies of segmental mobility of polymeric, liquid-crystalline materials as a function of external electric or electromagnetic perturbation have proved of scientific and industrial interest and will be discussed in some detail. 

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