Reducible domain

Fig.49 Composition distribution dependence of reduced domain spacing, D/D0, of PS- -P2VP with single microphase-separated structure. Do = 60.8 nm is domain spacing of parent copolymer with Mn = 125 kg/mol. Hatched region macrophase separation. From [160], Copyright 2003 American Chemical Society...

Figure 5 For H20 (a) wideband absorption frequency dependence (b) total loss spectrum (c) partial absorption contributions (1-4) (d) partial loss contributions (1-4) (e) is similar to (c) but for a reduced, domain, and on a linear ordinate scale (f) is similar to (d) but on a reduced ordinate scale, (g) comprises the partial contributions to the Raman spectra in the R (v) representation (h) in the Bose-Einstein representation.

The second solution is to reduce the size of the experimental domain. Usually the smaller the domain, the less the total curvature, and therefore there exists a simpler satisfactory model within the reduced domain. Third- or higher-order designs are rarely used (except for mixture models) and for the quadratic model to be sufficient the extent of the experimental region must normally be restricted. 

The last possibility allows us to define a point of interest, which may not be a true optimum if the system shows deviations from the model. The approximation may be adequate for practical purposes, and failing that it is likely to be a good centre point for a new experimental design in a reduced domain. 

However, following the choice of a profile and new limits for the excipients, a D-optimal design could be set up in a reduced domain and the formulation optimized (perhaps taking into account other properties besides the dissolution profile). In the following two sections we will see how good designs for RSM may be obtained for an irregular domain. 

Kurosaki, F. (1996) Effect of NADPH associated keto-reducing domain on substrate entry into 6-hydroxymellein synthase, a multifunctional polyketide synthetic enzyme involved in phytoalexin biosynthesis in carrot Arch. Biochem. Biophys. 328, 213-217... 

Polyvinyl chloride blends with HDPE had coarse domains and brittle properties. Slurry chlorination of HDPE attacked only the amorphous phase, producing a block copolymer, which then compatibilized the PVC-I-HDPE blends, reducing domain size and increasing ultimate elongation [31]. 

These blends with LDPE were weak and brittle. Adding chlorinated polyethylene, or PE grafted with 26% methyl methacrylate, greatly reduced domain size and increased ultimate elongation [31,107]. Adding hydrogenated polybutadiene-b-styrene-acrylonitrile-b-polybutadiene reduced domain size, increased interfacial adhesion, and improved mechanical properties [204b]. 

These blends with LDPE are sometimes reported as incompatible [110], at other times praised for their benefits. For example, addition of 10% of LDPE more than tripled impact strength [205] and LDPE has been reported to improve ultimate tensile strength and elongation, impact strength, water resistance, and dimensional stability [108,109]. In one study, blends were compatibilized by adding a terpolymer of ethylene/vinyl alcohol/vinyl mercaptoacetate, which reduced domain size and improved mechanical properties [202]. 

For example HDPE -b polystyrene was compatibilized by adding up to 1.5% of ethylene-styrene tapered block copolymer, reducing domain size and increasing impact strength and fracture toughness [55, 56]. For another example, EPR -b polystyrene was compatibilized by styrene-ethylene/butylene... 

LDPE -I- polystyrene was compatibilized by its graft copolymer, which reduced domain size and increased interfacial adhesion [10]. 

HDPE-I-butadiene/acrylonitrile rubber was compatibilized by adding maleated HDPE, which reduced domain size, strengthened the interface, and increased tensile and impact strength [61, 62]. 

PET PS Isobutylene- MA (IMA) copolymers Phenol substituted IMA (PIMA) copolymers PIMA better than IMA in reducing domain size and enhancing blend strength 119... 

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