In this paper, chemical functionalization of poly(lactic acid) (PLA) was carried out by using of salicyl aldehyde (SAl) and salicylic acid (SAc) as co-initiators of ring opening polymerization (ROP). Two factorial designs (22) were performed to evaluate the effects of the lactide/catalyst and co-initiator/catalyst molar ratios on the content of aldehyde or carboxylic acid end groups, thermal properties and molecular weight (Mw) of PLA. Tin(II) 2-ethylhexanoate was used as a catalyst. The co-initiator/catalyst molar ratio has a statistically significant influence on the polymer functionalization. The highest co-initiator/catalyst molar ratio of 12/1 allows the best aldehyde or carboxylic acid functionalization, independent on the lactide/catalyst molar ratio. On the other hand, the used lactide/catalyst and co-initiator/catalyst molar ratios did not show a statistically significant influence on the polymer thermal properties. Besides, co-initiator/catalyst molar ratio has a statistically significant influence on the polymer molecular weight. So, the highest co-initiator/catalyst molar ratio used (12/1) in combination with the highest lactide/catalyst ratio (125/1) produced functionalized PLA with higher molecular weights.
Keywords:
poly(lactic acid); ring opening polymerization; end group functionalized PLA; experimental design
