Free amorphous regions

Tsuji, H. and Miyauchi, S. (2001) Poly(L-lactide). 6. Effects of crystaUinity on enzymatic hydrolysis of poly(L-lactide) without free amorphous region. Polymer Degradation and Stability, 71, 415-424. 

To study the enzymatic degradation of the free amorphous region, completely amorphous PLLA thin film was prepared (see Section 22.3.2), and the erosion rate was directly monitored by using QCM in the nanogram per square centimeter regime [74]. The enzymatic erosion rate was dependent on the concentration of proteinase K, and the thin amorphous film of lOOnm thickness was completely hydrolyzed in 20 min when the concentration of the enzyme was >100 qg/mL. During the course of enzymatic degradation, even if the enzyme solution was replaced with a buffer solution (i.e.. 

PVF displays several transitions below the melting temperature. The measured transition temperatures vary with the technique used for measurement. T (L) (lower) occurs at —15 to —20 " C and is ascribed to relaxation free from restraint by crystallites. T (U) (upper) is in the 40 to 50°C range and is associated with amorphous regions under restraint by crystallites (63). Another transition at —80° C has been ascribed to short-chain amorphous relaxation and one at 150°C associated with premelting intracrystalline relaxation. 

Treatment of ceUulose with acids results in preferential hydrolysis in the more accessible amorphous regions and produces a product known as microcrystalline ceUulose (MCC). MCC is used to prepare fat-free or reduced-fat food products, to strengthen and stabilize food foams, as a tableting aid, and as a noncalotic bulking agent for dietetic foods. It has GRAS status. 

In polymer electrolytes (even prevailingly crystalline), most of ions are transported via the mobile amorphous regions. The ion conduction should therefore be related to viscoelastic properties of the polymeric host and described by models analogous to that for ion transport in liquids. These include either the free volume model or the configurational entropy model . The former is based on the assumption that thermal fluctuations of the polymer skeleton open occasionally free volumes into which the ionic (or other) species can migrate. For classical liquid electrolytes, the free volume per molecule, vf, is defined as ... 

The core of the crystalline region of irradiated PE contains residual free radicals. These diffuse slowly to the interface with the amorphous region. 

The core of the crystalline region of irradiated PE contains residual free radicals. These diffuse slowly to the interface with the amorphous region, where, in the presence of dissolved oxygen, whose equilibrium concentration is maintained by diffusion, they initiate an autooxidative chain of degradation.89 Postirradiation annealing in an inert atmosphere at a temperature above the alpha-transition temperature (85°C) leads to a rapid mutual reactions of the free radicals and eliminates the problem.90... 

Most polymers used as photoresists are amorphous. If, however, the polymer is capable of crystallization, the free volume relationship described in Figure 2 will be obeyed only by the amorphous regions. The crystalline regions will have... 

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