Esterification of styrene–maleic anhydride copolymer by mixed alcohols

A copolymer (MW = 1800) of styrene (St) and maleic anhydride (MAn) was esterified with an excess amount of an alcohol mixture, and then the relation between the esterification rates of the individual alcohols and the contents of the esters in the esterific copolymer was examined. At first, the rate constant of an individual esterification was obtained for four different alcohols ( n ‐butanol, i ‐amylalcohol, and benzylalcohol) in a noncatalyst system. Then, the mixed esterification of n ‐butanol and i ‐amylalcohol was carried out; from the analysis of the ester contents, the following equation was obtained:$$ {{\left[ {{\rm P}_{\rm 1} } \right]} \mathord{\left/ {\vphantom {{\left[ {{\rm P}_{\rm 1} } \right]} {\left[ {{\rm P}_{\rm 2} } \right]}}} \right. \kern-\nulldelimiterspace} {\left[ {{\rm P}_{\rm 2} } \right]}} = {{k_1 \left[ {{\rm B}_{\rm 1} } \right]_0 } \mathord{\left/ {\vphantom {{k_1 \left[ {{\rm B}_{\rm 1} } \right]_0 } {k_2 \left[ {{\rm B}_{\rm 2} } \right]_0 .}}} \right. \kern-\nulldelimiterspace} {k_2 \left[ {{\rm B}_{\rm 2} } \right]_0 .}} $$ From this result, it was concluded that, in esterification with alcohols involving n species, the content of the individual ester can be expressed by the following equation:$$ {{\left[ {{\rm P}_j } \right]} \mathord{\left/ {\vphantom {{\left[ {{\rm P}_j } \right]} {\sum\limits_{i = 1}^n {\left[ {{\rm P}_i } \right]} }}} \right. \kern-\nulldelimiterspace} {\sum\limits_{i = 1}^n {\left[ {{\rm P}_i } \right]} }} = {{k_j \left[ {{\rm B}_j } \right]_0 } \mathord{\left/ {\vphantom {{k_j \left[ {{\rm B}_j } \right]_0 } {\sum\limits_{i = 1}^n {k_i \left[ {{\rm B}_i } \right]_0 } }}} \right. \kern-\nulldelimiterspace} {\sum\limits_{i = 1}^n {k_i \left[ {{\rm B}_i } \right]_0 } }} $$ where [P] = concentration of esters in the copolymer, [B] 0 = initial concentration of alcohols, and k = rate constant of esterification ( i , j = 1,2…, n ).