Viscosity-increasing agents anhydride

The tendency for alternation of monomers in a styrene-maleic anhydride and styrene-acrylonitrile copolymers at moderate temperatures has been attributed to the formation of a charge transfer complex (CTC) between a donor (D) and an acceptor (A). This CTC is readily detectable by UV or nmR spectroscopy. More important, the equilibrium constant decreases as the temperature is increased and this effect can be followed by instrumental analysis. Thus it is possible to extrapolate to a higher temperature at which the CTC does not exist (16). Thus, by proper temperature control, it is possible to produce SMA alternating copolymers, block copolymers of vinyl monomers with both alternating and random SMA (17) and completely random copolymers of SMA (18). Half esters of SMA have been used as viscosity control agents in petroleum crudes (19). 

Almost quantitative carboxyl formation is observed if the polymer is converted to an intermediate Grignard (171) compound. The CO2 is added rapidly, accompanied by a significant increase in viscosity of the monofunctional polymers and gelling of the bifunctional polymers. Yields depend on the reaction rates and on stirring efficiency. Alternatively, a anhydride can be used as termination agent (reaction 41). 

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