DSC studies

In most of the studies discussed above, except for the meta-linked diamines, when the aromatic content (dianhydride and diamine chain extender), of the copolymers were increased above a certain level, the materials became insoluble and infusible 153, i79, lsi) solution to this problem with minimum sacrifice in the thermal properties of the products has been the synthesis of siloxane-amide-imides183). In this approach pyromellitic acid chloride has been utilized instead of PMDA or BTDA and the copolymers were synthesized in two steps. The first step, which involved the formation of (siloxane-amide-amic acid) intermediate was conducted at low temperatures (0-25 °C) in THF/DMAC solution. After purification of this intermediate thin films were cast on stainless steel or glass plates and imidization was obtained in high temperature ovens between 100 and 300 °C following a similar procedure that was discussed for siloxane-imide copolymers. Copolymers obtained showed good solubility in various polar solvents. DSC studies indicated the formation of two-phase morphologies. Thermogravimetric analysis showed that the thermal stability of these siloxane-amide-imide systems were comparable to those of siloxane-imide copolymers 183>. 

Siloxane-(methyl methacrylate) networks showing high oxygen permeabilities were prepared by gamma-irradiation of tx,(o-methacryloyl terminated tetramethyl-disiloxanes and methyl methacrylate 325). Due to the utilization of very low molecular weight disiloxane modifier, no phase separation was observed in the networks produced. DSC studies showed only one Tg around 120 °C. These materials were evaluated... 

FIGURE 31.2 Plots of crystalline melting point, heat of fusion and percent crystallinity of ethylene-vinyl acetate (EVA) samples versus (a) radiation dose (b) trimethylolpropane trimethacrylate (TMPTMA) level from differential scanning calorimetry (DSC) studies. (From Datta, S.K., Bhowmick, A.K., Chaki, T.K., Majali, A.B., and Deshpande, R.S., Polymer, 37, 45, 1996. With permission.)... 

The TG-DSC studies of Ba3BP30i2 Eu (Fig. 21.25), show that this compound is chemically stable and melts congruently at about 1111 °C. 

Vries et al. [3.59] described the development of a stable parenteral dosage form of the cytotoxic drug E 09. E 09 dissolves poorly in water and its solution is unstable. With the addition of 200 mg of lactose per vial containing 8 mg of E 09, an optimum formulation was developed with respect to solubility, dosage of E 09 and length of the freeze drying cycle. DSC studies have been used to select the most effective parameters. The freeze dried product remains stable for 1 year when stored at 4 °C in a dark environment. 

TG is a powerful adjunct to DSC studies, and are routinely obtained during evaluations of the thermal behavior of a drug substance or excipient component of a formulation. Since TG analysis is restricted to studies involving either a gain or a loss in sample mass (such as desolvation decomposition reactions), it can be used to clearly distinguish thermal events not involving loss of mass (such as phase transitions). 

Fig. 4.23. Cyclic DSC studies of the drug substance in Fig. 22 proving that the compound does not degrade at temperatures near or below 150°C.

E. L. Charsley, P. G. Laye, V Palakollu, J. J. Rooney, B. Joseph. DSC Studies on Organic Melting Point Temperature Standards. Thermochim. Acta 2006,446, 29-32. 

The morphology of the spherulites was in the form of a Maltese Cross , which was confirmed by the Avrami exponent value in the DSC study. The spherulite size of the binary blends was smaller than that of pure PET and PEN. 

Davio, S.R., K.M. Kienle, and B.E. Collins. 1995. Interdomain interactions in the chimeric protein toxin sCD4(178)-PE40 a differential scanning calorimetry (DSC) study. Pharm Res 12 642-648. 

Interpenetrating polymer networks of PMAA/PNIPAAm were prepared. The material exhibited both pH and temperature sensitivities. The temperature sensitivity was verified by DSC studies. The permeation studies showed a significant size exclusion phenomenon of the IPNs. The influence of pH and temperature on the IPN permeability was investigated. A hypothetical mechanism was presented to explain the high permeability at high temperature and high pH. 

DSC studies have shown that multifunctional monomers react quickly to form densely crosslinked networks from liquid monomer solutions. However, even a small amount of unreacted monomer can effectively plasticize a crosslinked network, rendering it more pliable. Eor this reason, mechanical analysis was combined with DSC studies to characterize the physical changes occurring in the proposed dimethacrylate system as polymerization proceeds. Static compression tests (Perkin-Elmer, DMA7e) were completed on disks (d = 11.5 mm, t = 1.7) immediately after they were irradiated for varied times. 

When conducting a differential scanning calorimetry (DSC) study on the stability of carbonaceous anodes in electrolytes, Tarascon and co-workers found that, before the major reaction between lithiated carbon and fluorinated polymers in the cell, there was a transition of smaller thermal effect at 120 °C, marked peak (a) in Figure 28. They ascribed this process to the decomposition of SEI into Li2C03, based on the previous understanding about the SEI chemical composition and the thermal stability of lithium alkyl carbonates.Interestingly, those authors noticed that the above transition would disappear if the carbonaceous anode was rinsed in DMC before DSC was performed, while the other major processes remained (Figure 28). Thus,... 

Hig purity /l-D-g uoosidase. The high purity em me grade for kinetic and DSC studies was prepared by a sequential HPSEC and HPIEC procedure, previously reported by Baker et iX. (77), using the Sephacryl S-200 and Mono-Q columns, respectively. This approach yields a -D-glucosidase preparation of approximately 99% purity by SDS-PAGE. 

Because of the availability of this remarkably extensive physical picture of the CBH I molecule (as well as the potential availability in adequate quantities of the purified enzyme itself), DSC studies can provide vduable insights into structure-function relationships for this important cellulase. We present here a comparison of DSC analyses of the intact CBH I molecule with those of the isolated catalytic-domain and tail-region proteolytic fragments. 

In the 80/20 specimens, the changes in E (rt) follow a different pattern. There is little change in E (rt) up to a dose of 2000 Mrads. Between 2000 and 4000 Mrads, E (rt) decreases 13%. At 10,000 Mrads, E (rt) is almost 9% greater than a control. Previous DSC studies have shown that during the first 2000 Mrads, there is substantial additional cure (14). Competition between chain scission of strained bonds and further curing reactions could "balance out"... 

Results from Differential Scanning Calorimetry (DSC) studies of this system display low and high temperature exotherms occurring at approximately 130 °C and 255 °C respectively. (2,3) The DSC data from reference 2 is reproduced here as Figure 2. On the basis of the NMR results explained below, the following addition reaction of 1 to 2 producing the soluble prepolymer is expected to correspond to the low temperature exotherm (2,3) ... 

Initial studies were performed with [f-Bu2GaSbEt2]2 (3). DSC studies showed 3 to decompose in two steps around 190 and 215 °C as was confirmed by TGA/DTA experiments (Fig. 12) [36]. The first mass loss of almost 37% is only slightly larger than the calculated mass loss due to the elimination of two Ga-(t-Bu) groups (34%). Between 200 and 220 °C, an additional 9% mass loss was observed. Finally, a third mass loss of about 4% takes place above 500 °C, that most likely results from some decomposition of the material formed. 

DSC studies have shown that modification alters thermal transition temperatures and the overall enthalpy (AHgei) associated with gelatinization (Tables 10.13 and 10.14). Upon hydroxypropylation, the reactive groups introduced into the starch chains are capable of disrupting the inter-and intra-molecular hydrogen bonds, leading to an increase in accessibility by water that lowers... 

Morikawa, K., Nishinari, K. (2000a). Rheological and DSC studies of gelatinization of chemically modified stareh heated at various temperatures. Carbohydr. Polym., 43,241-247. 

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