منابع مشابه
Modeling the viscoelastoplastic behavior of amorphous glassy polymers
Constitutive equations are derived for the viscoelastoplastic response of amorphous glassy polymers at isothermal loading with small strains. A polymer is treated as an ensemble of cooperatively relaxing regions (CRR) which rearrange at random times as they are thermally agitated. Rearrangement of CRRs reflects the viscoelastic response of the bulk medium. At low stresses, CRRs are connected wi...
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A study of the microstructure of polymers is essential for the understanding of their anomalous diffusion properties. The concept of free volume may be utilized to study relaxation phenomena and diffusion processes in polymers. Since a quantitative definition of free volume is not possible, a new concept called available volume is introduced. A simple geometric definition of available volume, r...
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The influence of crystallinity on exciton diffusion and fullerene distribution was investigated by blending amorphous and semicrystalline copolymers. We measured exciton diffusion and fluorescence quenching in such blends by dispersing fullerene molecules into them. We find that the diffusion length is more than two times higher in the semicrystalline copolymer than in the amorphous copolymer. ...
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Irbesartan (IBS) is a hydrophobic drug with poor aqueous solubility and dissolution rate. Solid dispersions (SDs) of IBS were prepared with both small molecules (tartaric acid and mannitol) and polymeric additives (polyvinyl-pyrrolidone, PVP, and hydroxypropyl methylcellulose, HPMC). A 9.5 and 7 folds enhancement in solubility over the crystalline form (14.6 microg mL-1) was observed for tartar...
متن کاملOn the Equivalence Between the Thermodynamic and Dynamic Measurement of the Glass Transition in Confined Polymers
Understanding why the glass transition temperature (Tg) of polymers deviates substantially for the bulk with nanoscale confinement has been a 20-year mystery. Ever since the observation in the mid-1990s that the Tg values of amorphous polymer thin films are different from their bulk values, efforts to understand this behavior have intensified, and the topic remains the subject of intense resear...
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تاریخ انتشار 2005