Thermal properties, methyl-substituted

Properties. MethylceUulose [9004-67-5] (MC) and its alkylene oxide derivatives hydroxypropylmethylceUulose [9004-65-3] (HPMC), hydroxyethylmethylceUulose [9032-42-2] (HEMC), and hydroxybutyknethylcellulose [9041-56-9] (HBMC) are nonionic, surface-active, water-soluble polymers. Each type of derivative is available in a range of methyl and hydroxyalkyl substitutions. The extent and uniformity of the methyl substitution and the specific type of hydroxyalkyl substituent affect the solubifity, surface activity, thermal gelation, and other properties of the polymers in solution. 

Aliphatic hyperbranched polyesters, 56 Aliphatic isocyanate adducts, 202 Aliphatic isocyanates, 210, 225 Aliphatic polyamides, 138 Aliphatic polyesteramides, 56 Aliphatic polyesters, 18, 20, 29, 32, 87 degradable, 85 hyperbranched, 114-116 melting points of, 33, 36 structure and properties of, 40-44 syntheses of, 95-101 thermal degradation of, 38 unsubstituted and methyl-substituted, 36-38... 

The effect of substituents on the thermal properties of a series of aromatic azoxy polymers is shown in Table 3, Polymers 10-12, in which it is seen that the introduction of methyl groups into the mesogenic units resulted in a depression in both the melting point and the clearing temperature of the polymer. As can be seen from these data, the substitution position in the mesogenic unit is also important, but it will be necessary to have much more experimental results before the positional effect may be evaluated systematically. 

For our series of copolymers, no strong Influence by N-methyl substitution on the thermal properties is observed until the degree of substitution exceeds 25 mole percent. 

Gas Barrier and Thermal Properties of (Alkylsulfonyl)methyl-Substituted Poly(oxyalkylene)s... 

Study of the bulk viscoelastic properties of 11a are hampered by the crystallinity of the material, even though crystallization is slow. By introducing linkers with a mixed methyl substitution pattern, noncrystallizing supramolecular polymer 11b was obtained, which was studied using dynamic mechanical thermal analysis (DMTA), rheology, and dielectric relaxation spectroscopy [20]. 

The second method is based on the use of polyimides with lower glass transition temperatures that can be melt-processed. For example, intrinsically photosensitive preimidized polymers formed by reacting 3,3 4,4 -benzopheno-netetracarboxylic acid dianhydride (BTDA) with methyl-substituted 4,4 -methylenebisbenzeneamine (MDA), blended to epoxy resins, give high strength laminate with copper. Poly(isoimides), which exhibit good melt-flow properties before thermal isomerization to imides, are also used to make flexible circuits. In the last process copper is electroless plated on polyimide film such as Kapton 200H. 

The thermal stability, as well as structure-related properties, such as resistivity and elasticity, of polysiloxanes is dependent on the nature of the pendant groups on the silicon atoms. Thus high-molecular-weight polydimethylsiloxanes are attacked at temperatures near 200 °C in the presence of oxygen, but substitution of a phenyl group for one methyl group raises the oxidative stability to 225 °C. 

General properties of oligosilanylsulfanes selectively may be altered by variation of the R-groups on sulfur. The methyl derivatives, for instance, are colorless liquids, which can be distilled without decomposition, while the 2-naphthyl substituted compounds are non volatile crystalline solids. If R = Ph or Ph3Si, the reaction products are obtained as viscous oils, which cannot be purified further because of their thermal and hydrolytic lability. 

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