Poly , thermal transition

Allcock HR, Mang MN, Dembek AA, et al. Poly[(aryloxy)phosphaz enes] with phenylphenoxy and related bulky side groups, synthesis, thermal transition behavior, and optical properties [J]. Macromolecules, 1989, 22, 4179 190. 

Yokoyama, T. Hiraoko, K. (1979). Hydration and thermal transition of poly(acrylic acid) salts. Polymer Preprints of the American Chemical Society, Division of Polymer Chemistry, 20, 511-13. 

The synthesis of poly(anhydride-co-amide)s (Table VII) of various chemistries was pursued by Hartmann and Schulz (1989) as a means of improving biocompatibility and extending the degradation times of polyanhydrides. This work also contains calorimetry data on the thermal transitions and spectroscopic characterization. 

With heating from 5 to 45°C, thermal changes in conformation in the major /3-casein are observed by spectral methods (Garnier 1966). From measurements of the optical density at 286 nm and of the specific optical rotation at 436 nm, a rapidly reversible endothermic transition (AH 30 kcal/mole) with a half-transition temperature of 23-24°C is observed. The optical rotatory dispersion data suggest a decrease in the poly-L-proline II structure (12 to 5%) and a slight increase in a-helix (11 to 16%) with increasing temperature. This transition probably occurs prior to association, since it is rapid, and the carboxyacyl derivative of the monomer, which does not polymerize with increasing temperature, also demonstrates the optical rotatory disperson thermal transition. 

DSC and DTA. They can be used to confirm suspicious glass transitions revealed by DSC and most important, they can further quantify molecular mobility associated with sub-glass transitions. For example, DSC analysis of poly (ethylene 2,6-naphthalene dicarboxylate) (PEN) only revealed the presence of a glass transition around 112 °C (Hardy et al., 2001). DMA analysis of the same sample, however, revealed two secondary relaxations below this glass transition (Hardy et al., 2001). In the case of humic materials, it is not uncommon for DSC to fail to detect clear thermal transitions due to their heterogeneous nature, which contributes to overlap/ broadening or washout of thermal transitions. As such,TMA and DMA represent powerful, complementary tools to DSC. 

In another study, it was successfully reported an intimate ternary blend system of poly(carbonate) (PC)/poly(methyl methacrylate ) (PMMA)/poly (vinyl acetate) (PVAc) obtained by the simultaneous coalescence of the three guest polymers from their common y-cyclodextrin (y-CD) inclusion complex (IC). The thermal transitions and the homogeneity of the coalesced ternary blend were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) [50]... 

Miyashita et al. carried out miscibility characterization of CA blends with poly(N-vinyl pyrrolidone) (PVP), poly(vinyl acetate) (PVAc), and poly(N-vinyl pyrrolidone-co-vinyl acetate) random copolymers [P(VP-co-VAc)s] [ 104]. On the basis of thermal transition data obtained by differential scanning calorimetry (DSC), a miscibility map (Fig. 8) was completed as a function of the degree of substitution (DS) of CA and the VP fraction in P(VP-co-VAc). Figure 9 compares results of the DSC measurements between two blending pairs of CA/P(VP-co-VAc) corresponding to the polymer combinations marked as A and B in Fig. 8. In the data (Fig. 9b) for the blends of CA (DS = 2.95) with P( VP-co-VAc) of VP = 51 mol %, we can readily see a sign of poor miscibility, as is evidenced from the lack of an appreciable shift in the... 

The interaction of tilorone hydrochloride with native DNA stabilizes the double helical structure of the macromolecule towards thermal denaturation. The effect of tilorone hydrochloride on the thermal denaturation of DNA s from various sources having different base composition has been studied28. At a drug to DNA-P molar ratio of 0.21, the Arm increased with increasing AT content of the DNA. This observation indicates that tilorone hydrochloride perferentially binds to the dAT portions of the DNA molecule. This is confirmed by the strong effect of tilorone hydrochloride on the thermal transition temperature of poly d (A-T), ATm = 29 °C. 

Table 5 Molecular weight characteristics and thermal transitions of poly-VII and poly-VIII ...

In contrast to that, the short fluorinated side groups of poly-XIII did not lead to thermotropic LC phases, but resulted in microphase-separated block copolymers caused by the hydrophobic and oleophobic character of fluorinated polymers. This interpretation was supported by DSC data, which gave the thermal transitions for both blocks. 

Tablets Molecular weight and thermal transitions for poly-(XXIII-m-n) ...

Molecular weights and molecular weight distributions, together with the thermal transitions of poly-XXIII-m-n are summarized in Table 15. From these data it can be concluded that inducing smectic layering requires a minimum of eight methylene units and three difluoromethylene units or three methylene units and four difluoromethylene units. All other polymers with m=3,4 exhibited nematic mesophases. Polymers with m=2 displayed only nematic mesophases, or in the case of n=3 no mesophase at all. Because of the thermal transition data, the authors concluded that the polymers were not microphase-separated. 

Table 17 Molecular weights and thermal transitions of poly-XXVII and poly-XXVII- 7-BA...

The same group reported on the synthesis and characterization of all-hydrocarbon MCLCPs, poly-(XXXX), and their hydrogenated derivatives poly-(XXXXI), based on 4,4 -bis(a-co-alkenyl)-l,r-biphenyl derivatives, see Fig. 23. Monomers with different a-co-alkenyl chain lengths were used to prepare not only the corresponding homopolymers but also statistical copolymers. Crystallinity, thermal transition properties and LC properties were studied. 

The theoretical treatment of Zimm and Bragg has also been applied to the shallow thermal transition of poly-L-lysine, in which the variation of helical content as a function of temperature has been obtained from rotatory dispersion measurements (Applequist and Doty, 1961). If one assumes that the parameter o- is the same as for poly-y-benzyl-L-glutamate, it is then possible to obtain the heat per residue for the formation of the helix of poly-L-lysine. The small magnitude of this result, between —50 and —80 cal/mole near pH 10, as compared to the enthalpy of the hydrogen bond estimated... 

Figure 2.33 Variation of thermal transition temperatures of poly(vinyl chloride) with plasticizer content.

To date, poly(ferrocenylgermanes) have been much less studied than the silicon analogs, and they represent an interesting area for future work. Nevertheless, their thermal transition behavior has been explored (Table II) (57). Studies of the electrochemistry of the poly(ferrocenylgermane) 20 (R = R = Me) have shown that this material exhibits two reversible oxidation waves in CH2CI2, which indicates that the iron atoms interact with one another in a similar way to poly(ferrocenylsilanes) 63). 

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