Blocky character

The hydrophobic charge on the interface, which is fundamental for the polymer adsorption, increases with increase in the residual acetate content and the blocky character of acetate groups. This fact is contrary to the aim of wanting large particles because of the simultaneous reduction in interfacial tension [42]. 

Another approach toward preparing PLCs involves direct copolymerization of monomers or macromonomers under variable solubility conditions. This method is based on selective solubility of the two monomers leading to a egation of the monomers and resulting in more blocky character of the resultant RCP. In early studies, Lozinsky et reported on... 

PBD has some blocky character. An explanation of this effect is that the (f-orbitals of the sulphur atom in a modified PBD unit overlap the re-orbitals of an adjacent double bond and thus activate it towards electrophilic attack of another sulphenyl chloride molecule (Scheme 5). This theory predicts that... 

When the reaction is carried out in the solid state, chlorination begins in the amorphous areas and on crystalline surfaces due to the chlorination there is a progressive disorganization of crystalline areas. When the reaction is carried out at room temperature, traces of crystallinity persist until the chlorine content reaches 60% this explains the blocky character of the chlorination. Such a blocky character is observed when the reaction is carried out on a suspension of PE in a liquid or in a fluidized bed chlorination in aqueous suspension is the most widely used commercial process. 

This effect can be explained in the following way the d orbitals of the sulfur atom in a modified polybutadiene unit overlaps the n orbital of an adjacent double bond and activates it towards electrophilic attack of another sulfenyl chloride molecule (Scheme 36). This mechanism is supported by the fact that the substitution of the more strongly bridging alkylthio group for an arylthio group enhances the anchimeric effect and increases the blocky character of the resulting copolymer, as shown in experiments carried out with methanesulfenyl and n-butanesulfenyl chlorides. 

Such procedures are nevertheless highly empirical in character and until recently the formation of blocky structures could be inferred qualitatively only from observations of thermal transitions and crystal character, and quantitatively only from simple and often insensitive analyses. For wholly amorphous copolymers, only the latter method was available. 

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