Melting behaviours of poly(oxytetramethylene)glycols (POTMGs) with different molar masses were investigated by temperature-modulated
differential scanning calorimetry (TMDSC) and relaxation times within the melting range were estimated from the modulation-frequency
dependence of phase angle δ. An Arrhenius plot of the relaxation times exhibited a plateau in the lower melting peak region
of POTMGs with molar masses of 1400, 1000 and 650. This plot was compared with the standard DSC curve. The apparent activation
energy was estimated from the relaxation time in the upper and lower sides of a melting temperature region: slight dependence
on the molar mass was observed for the former region whereas the maximum value was obtained for a molar mass 1400 for the
Summary A double endothermic peak appears in the DSC curve of a PTHF oligomer. In order to investigate this phenomenon, a two-component blend of PTHF was prepared with a number average molecular mass of M=1400, and the double endothermic phenomena were investigated by TM-DSC. The larger the amount of the long chain component in the PTHF blend, the smaller the difference between the Cp-T curve and the normal DSC curve. The amounts of endothermic energy ?Hendo,1, ?Hendo,2 and exothermic energy ?Hexo,1, ?Hexo,2 in each peak at infinite modulation frequency were estimated.
Poly(2-hydroxymethyl methacrylate) (PHEMA) suspension in anisole shows temperature dependent iridescence between 0 and 60C.
To reveal the mechanism of the temperature-dependent iridescence, PHEMA-anisole mixtures were prepared, and their thermal
behaviors have been studied by dynamic DSC (DDSC) technique. All the mixtures showed a broad peak at 325 K on loss part of
DDSC curves (loss Cpcurve), and showed a gentle step change between 250 and 340 K on the storage part (storageCp curve). A temperature region of these changes matched the observation of iridescence change. Temperature of the step change
depended on the composition of mixture. The temperature dependence of iridescence of the polymer mixture has been attributed
to the conformational changes of PHEMA chains.
differential scanning calorimetry, the melting behaviour of poly(oxytetramethylene)-alt-(aromatic oligoamide) (POTM-alt-AOA)
has been studied in comparison with that of polyoxytetramethylene glycohols
(POTMGs). The apparent melting temperature of the block copolymers is found
to be less than that of the corresponding POTMGs by approximately 30°C.
The relaxation time of melting of a POTM segment has been estimated and compared
with that of POTMG. The relaxation time of POTM-alt-AOA
is slightly shorter than that of POTMG when the molar mass of the POTM segment
is 2900; however, it is longer when the molar mass is 1400.
TG and DSC were carried out on PMAA-net-POTM in order to elucidate the relation between the heterogeneity and the thermal
changes; moreover, TG and DSC were carried out on PPOTMDM and PMAA to compare the results. The onset temperature in the last
stage in the TG curve of PMAA-net-POTM increases as the concentrations of DMF and POTMDM in the polymerization decrease. This is explained in terms of plasticizers
effects. A single peak due to fusion of POTM chains appears in the DSC curves of most copolymers. However, it is not seen
in the DSC curves of copolymers with high heterogeneity. This is explained in terms of the freezing of POTM chains by frozen
Authors:M. Tsuchiya, M. Ishii, T. Kojima, and Y. Oohira
Thermal behaviors of POTMDM-net-PMMA and POTMG/PMMA blends were studied by DDSC. Tg of the polymer network was lowered by increasing the POTMDM in feed for copolymerization of POTMDM and MMA. A crystallization
peak was observed only when MMA in feed was less than 30%. Tg of POTMG/PMMA was also lowered by decreasing the content of PMMA, however, the change was observed only when PMMA content
was more than 70%. These results suggest that thermal transitions of the polymer network are restricted by the mesh size.
POTM chains of the polymer network effectively play as a plasticiser.
Authors:T. Fujimura, N. Sarugaku, M. Tsuchiya, K. Ishimaru, and T. Kojima
The TG analyses are given for variously meta- and/or para-linked aromatic polyamides with various benzimidazolyl (BI)contents.
The TG curves of the polymers were evaluated within 600C by use of an equation for multiple events. The TG curves of BI-substituted
polymers are expressed for triple events, though the TG curves of unsubstituted polymer are expressed for double events. The
amount of residue of BI-substituted polymers at 800C is larger than that of unsubstituted polymers, perhaps because moieties
concerning BI degrade at higher temperatures.
Authors:W. Miyano, E. Inoue, M. Tsuchiya, K. Ishimaru, and T. Kojima
DSC studies are given for polytetrahydrofurans with molecular masses equal to 650, 1400, and 2900, for their blends, and for
their cured samples. The samples were stored, annealed, and quenched to obtain the samples with different thermal histories.
Two or more endothermic peaks appear in the DSC curves for the stored samples, even for the non-blended samples. A hyperbolic
curve forced the plot of the highest melting temperature vs. the molecular mass to asymptote to about 50C. The relationship
between the highest melting temperature and the composition for the blended samples is suitable to linear or Fox’s relation.
A peak and a shoulder appear in the DSC curves of the cured samples. As the samples are cooled at the faster rates in the
thermal treatment, the shoulder appears at the lower temperatures.
Authors:H. Abematsu, M. Tsuchiya, Y. Iseri, and T. Kojima
The TG studies are presented for isomers of benzimidazolyl-substituted polyamides (BIPA). The TG data are compared with those
polyamides (PA) of identical backbones without substitution, in view of the mechanism of thermal degradation. The TG mass
loss curves divided to three temperature ranges reflect the decomposition reactions in the respective temperature ranges:
(1) cleavage of single bonds of nitrogen to aromatic ring, (2) random scission of single bonds, (3) condensation of the remained
rings. Liberation of benzimidazole rings occurs in the temperature range (2). The final product, char, contains benzimidazole
rings. Terephthaloyl-rich BIPA's retard liberation of benzimidazole from the decomposed polymer.