DEPT135 was used to study the hydroxymethylation of p-cresol in basic condition. The roles of type and amount of catalyst, reaction temperature, reaction time were investigated to optimize reaction conditions for the synthesis of 2,6-dihydroxymethyl-4-methyl phenol(2,6-DHMMP). Subsequently, a series of novolac resins with extremely high or low M W , narrow M W /M N , as well as alternating co-condensation structure have been produced by the condensation of 2,6-DHMMP and phenol, m-cresol etc. The synthesized p-cresol/phenol resin has a M W of 20000-30000, and M W /M N of 15-20, and also excellent resistance to alcohol and alkali, which meet the needs of photosensitive compositions. The synthesized p-/m-cresol resin has a M W of 25000, and M W /M N of below 15, as well as well resistance to alkali, heat and etching. These novolac resins have good prospects in terms of resist and printing plates.
Chemical shifts of aromatic carbons of phenolic compounds used in novolac synthesis commonly were recorded in aqueous alkaline solution and the results indicated that chemical shifts of para-position carbon was lower than that of ortho-position carbon, both of which were lower than that of meta-position carbons. Hydroxymethylation of some phenolic compounds with formaldehyde catalyzed by sodium hydroxide were investigated also. The research showed that hydroxymethylation could both occur at ortho-and parapositions, and occur at para-position more easily. Moreover, hydroxymethylated produts were stable in basic conditions compared with in acidic conditions. In summary, in basic conditions the lower the chemical shift of reactive site of phenolic compounds, the more easily the hydroxymethylation of the reactive site. Therefore, electrophilic substitution reaction of phenolic compounds in basic conditions can be predicted by chemical shift of reactive site. According to the regulation, a stepwise base-acid catalyzed reaction was used to synthesize various series of novolac with high Mw and low Mw/Mn, all of which have good application prospects in the field of direct digital plate-making and resists for LCD and IC.
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