Copolymer chemically homogeneous

All polymers were prepared with ethyl azodiisobutyrate in ethyl acetate at ca. 77 °C and a concentration of ca. 50% unless otherwise specified. Chemically homogeneous copolymers were prepared with a maximum 3 mole % scatter in composition. Following stabilization they were isolated by partial distillation and reprecipitation. 

It is possible to consider a natural equimolar MMA-BA copolymer as consisting of a multitude of adjacent chemically homogeneous copolymers with a composition from 70 to 0 mole % of MMA. Investigations of model mixtures composed of only two chemically homogeneous copolymers should give a first approximation. 

Mixtures of chemically homogeneous copolymers yield homogeneous films at Apmma below 25. 

To see whether or not knowledge of the behavior of binary mixtures of chemically homogeneous copolymers can be applied to natural co-... 

Figure 7. Confirmation of multiphase nature of natural copolymers (a,b) and chemically homogeneous copolymer (c)...

In practice, there are effective means for nearly eliminating the spread of chemical compositions (14). The essential condition for the formation of a chemically uniform copolymer is that the monomers must be maintained in the same ratio throughout polymerization. There are two procedures for maintaining this condition. First, it can be achieved by making a continuous addition of either the more reactive monomer alone or certain mixtures of the comonomers as the reaction proceeds. The second method of producing chemically homogeneous copolymers is to proportion a mixture of monomers whose composition is the same as that of the copolymer being formed. 

Compositional heterogeneity of the substituted PMMA For all systems investigated (36), the substituted PMMA are characterized by a fairly high chemical homogeneity over the whole range of DSm(DSm<0.76), quite comparable to that of a radical azeotropic S-MMA copolymer (40) (a = 1.6x10 ). The mean square standard deviation o related to two copolymers of DPn =... 

Mixtures of chemically homogeneous methyl methacrylate— n-butyl acrylate copolymers appear homogeneous optically (clear) and in torsional oscillation experiments (one damping maximum) for A MM A 10-25 mole %. There is no... 

Another important result was the finding that inhomogeneous binary mixtures of chemically uniform copolymers did not homogenize upon adding a third copolymer capable of forming clear films with each of the two mixture components. As Molau (4) already found in the styrene-acrylonitrile system there is no homogenization. ... 

Mixtures of chemically homogeneous methyl methacrylate-n-butyl acrylate copolymers are homogeneous for composition ranges be-... 

Similarly, a polymeric medium characterised by strong cohesion, is also obtained from di- or tri-block copolymers made by linking two or three chemically homogeneous sequences which are incompatible with one another usually, the Tg of one of the two sequences is above room temperature while it is below for the other sequence [10]. There is a phase separation glassy segments are connected to one another by amorphous segments and they play the role of ordered domains formed in semi-crystalline polymers. 

SEC with light-scattering detection direct copolymer molar mass measurement for chemically homogeneous and segmented copolymers independent of their structure. 

Based on previous oflF-line results by other authors (11, 12, 14), we anticipated improved resolution of multicomponent analytes. We also hoped for chemically homogeneous fractions to measure MMDs of copolymers and blends correctly. 

As stated in Chapter 1, the chemical structure of the top surface layers of a solid determines its surface properties. If these top layers consist of the same chemical groups, then the surface is called chemically homogeneous, and if they consist of different chemical groups it is called chemically heterogeneous. The presence of two or more chemically different solid substances in a surface layer enormously multiplies the possibilities for variety in the types of surface, such as copolymer surfaces and catalysts having many different atoms at the surface. The chemical heterogeneity of a surface is an important property in industry affecting catalysis, adhesion, adsorption, wettability, biocompatibility, printability and lubrication behavior of a surface, and it must be determined analytically when required. 

Most of the work in the field of polymer crystalhzation in the last decades has been done on long polymer chains like polyethylene, polypropylene, poly(ethylene oxide) or poly(ethylene terephthalate) which form folded-chain crystals with a typical thickness of about 10 nm [1-5]. In all these cases chain folding plays an important role and crystaUization starts from a chemically homogeneous melt. More recently, the confined crystaUization of polymers in small domains of microphase-separated block copolymers has attracted a lot... 

Brekner, M. J. Osan, R Rohrmann, J. Antberg, M. Process for the preparation of chemically homogenous cycloolefin copolymers. European Patent 0503422B1 (Targor GmbH), June 3, 1998. 

The structure of copolymers in terms of composition or sequence length distribution may vary between two extremes - copolymers with a very high level of chemical heterogeneity within each chain, and homogeneous copolymers with the comonomer units randomly distributed along the chain. 

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