Versatile Nature of Poly(Vinylpyrrolidone) in Clinical Medicine
P. Mereena Luke, K. R. Dhanya, Didier Rouxel, Nandakumar Kalarikkal, Sabu Thomas in Advanced Studies in Experimental and Clinical Medicine, 2021
PVP is soluble in all types of organic solvents and under normal conditions and is quite stable. The reason behind this remarked solubility is that they contain both hydrophilic and hydrophobic groups in the chain structure. The inert, hygroscopic, colorless, and temperature resistant behavior of PVP makes it a unique polymer [87, 88]. The glass transition temperature is related with its molecular weight. PVP films are fairly hard and transparent. Binding with natural as well as synthetic resins, PVP forms clear films. Chemically modified PVP are extremely inert in nature. In powder state, it is comparatively stable and if applying temperature on PVP, it becomes yellow in color. PVP is in contact with light, the formation of gelation happens.
Degradable, biodegradable, and bioresorbable polymers for time-limited therapy
Yoshinobu Onuma, Patrick W.J.C. Serruys in Bioresorbable Scaffolds, 2017
Some of these applications require macromolecules soluble in aqueous media, especially body fluids; some others must self-assemble in these fluids like micelles and aggregates. This is the domain of amphiphilic macromolecules. Last but not least, applications that require mechanical properties are relevant to thermoplastic polymers. The main phenomenon that commands the behavior of this class of materials and thus of polymeric biomaterials is the glass transition temperature, Tg. In practice, solid state properties of a prosthetic device depend very much on the position of Tg with respect to the temperature of exploitation of this device. Above Tg, a thermoplastic polymer is in the rubbery state and can be deformed more or less rapidly when submitted to mechanical stresses. Below Tg, the same solid polymer is rigid and resistant to stresses but it is brittle, i.e., it breaks at low degree of deformation. Tg is normally well defined for a given polymer. However, many factors can affect this transition, especially the presence or the uptake of plasticizing small molecules (plasticizers) that shifts it toward lower temperatures. Other compounds (fillers like carbon fibers, mineral radio-opacifiant, some drug particles, etc.) can be present that do not affect Tg because they are not compatible with the polymer. The body temperature being imposed, the Tg of a polymer must be below or above 37°C depending on whether one wants deformation or rigidity. When macromolecules are composed of monomer units repeated regularly, they can assemble in regular arrays and crystallize more or less partially, a physical semicrystalline state characterized by a melting temperature (actually a melting zone because macromolecules do not have the same length, a feature referred to as polydispersity) and a degree of crystallinity.
Binders in Pharmaceutical Granulation
Dilip M. Parikh in Handbook of Pharmaceutical Granulation Technology, 2021
The greater toughness and deformability of HPC also coincides with higher thermoplasticity as measured by thermal analysis. In contrast to other polymers, HPC at a typical equilibrium moisture content (~3%) exhibited a high-intensity glass transition in the low-temperature range (−3–0oC) (Table 4.12) [3,52]. Increased molecular mobility and plasticity are generally associated with lower glass transition. Overall, these results confirm a higher state of plasticization for HPC in relation to the other binders.
Preformulation studies of l -glutathione: physicochemical properties, degradation kinetics, and in vitro cytotoxicity investigations
Published in Drug Development and Industrial Pharmacy, 2020
Mengyang Liu, Manisha Sharma, Guo-Liang Lu, Naibo Yin, Murad Al Gailani, Sree Sreebhavan, Jingyuan Wen
Figure 4(b) shows the DSC curve of pure GSH, which has an endothermic peak at 195 °C corresponding to its melting temperature [28]. It followed with several small endothermic peaks at 210 °C, indicating the decomposition of GSH. The cooling cycle also confirmed the completed decomposition of GSH, as there are no recrystallisation peaks in cooling procedure. However, there was no exothermic peaks detected between 25 °C and its melting point, which indicates that the glass transition temperature (Tg) did not exist for GSH. Glass transition is defined as the reversible transition in amorphous materials or amorphous regions within semi-crystalline materials, from a hard and relatively brittle ‘glassy’ state into a viscous or rubbery state with increasing temperature [29]. The absence of Tg in the DSC curve indicates the crystalline nature of GSH, supporting the morphology characterization as described above.
Physical stability of dry powder inhaler formulations
Published in Expert Opinion on Drug Delivery, 2020
Nivedita Shetty, David Cipolla, Heejun Park, Qi Tony Zhou
DSC is another solid-state characterization technique which measures the glass transition temperature (Tg) and helps in the identification of melting, crystallization, degree of crystallinity and thermal transition phenomena. Glass transition temperature is the temperature at which a transition from a ‘glassy state’ to a ‘rubbery state’ occurs in an amorphous material. The unique advantage of the DSC technique is its rapid analysis time and that it requires only a nominal sample. However, two major disadvantages of using DSC for measuring Tg are its relatively low sensitivity and the possibility that multiple thermal events may occur and overlap or interfere with the determination of the glass transition [183]. To overcome these limitations of conventional DSC, the modulated DSC (mDSC) was introduced more than two decades ago and has been used to characterize amorphous solids [184]. Both DSC and PXRD can quantify moderate-to-high levels of amorphous materials whereas DVS is more sensitive and can detect very low amounts of amorphous content [48].
Cholecalciferol complexation with hydroxypropyl-β-cyclodextrin (HPBCD) and its molecular dynamics simulation
Published in Pharmaceutical Development and Technology, 2022
Fang Wang, Wenbo Yu, Carmen Popescu, Ahmed Ashour Ibrahim, Dongyue Yu, Ryan Pearson, Alexander D. MacKerell, Stephen W. Hoag
Thermograms of cholecalciferol, HPBCD, and cholecalciferol–HPBCD complex are shown in Figure 4. DSC is a thermal analysis technique that used to test the heat capacity (Cp) of materials with the temperature change. A crystal material will exhibit a melting or crystallization event associated with an enthalpy change. As the melting temperature (Tm) is reached, there will be an endothermic peak associated with the melting transition and this event shows up in the DSC curve. Amorphous materials do not have an organized solid state. When heating amorphous materials there is a second-order phase change in which the heat capacity abruptly changes, and this transition from the glassy to rubbery state is called the glass transition and is characteristic of amorphous materials. This transition is broad shift in the baseline of the DSC curve, and Tg is the glass transition temperature.
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