Synthesis and properties of chitosan‐modified poly(acrylic acid)

Abstract

Potassium persulfate (K 2 S 2 O 8 ) was used to initiate the polymerization of acrylic acid (AA) monomer in a chitosan (CS) solution. Both a poly(acrylic acid) (PAA) homopolymer and a CS-co-PAA copolymer were produced. When the amount of AA was increased from 5 to 40 g with 5 g of CS, the total monomer conversion was found to increase from 89 to 98% after 2 h of reaction at 708C. In addition, the percentage of reacted AA monomer being converted to the CS-co-PAA copolymer (copolymerization efficiency) and the weight composition of the PAA portion in the copolymer (copolymer composition) both increased with the amount of AA added. The structures and properties of the synthesized CS-modified PAA polymers were studied. In Fourier transform infrared spectra, the formation of a polyelectrolyte complex between CS chains and PAA chains could be observed. From the thermograms obtained via differential scanning calorimetry, we found that the presence of rigid CS chains increased the glass-transition temperature of PAA. Thermogravimetric analysis revealed three stages of degradation of the synthesized CS-modified PAA polymers. The swelling ratio of the CS-modified PAA polymers depended on the pH value and had a maximum value in a buffer solution at pH 7. This was due to the changes in the morphological structure with the pH value.

Synthesis of chitosan‐poly(Acrylic Acid) complex particles by dispersion polymerization and their applications in ph buffering and drug release

“…However, in the previous studies, it was found that the anionic sulfate radical ( • SO 4 − ) can degrade one CS chain into two shorter chains. One has a terminal carbonyl group and the other has a free radical at the scission end 27, 28. It is thus expected that if KPS was used to initiate the polymerization in the present system, it could also degrade CS and thus produce CS chain radical.…”

“…It is thus expected that if KPS was used to initiate the polymerization in the present system, it could also degrade CS and thus produce CS chain radical. Subsequently, AA was able to grow on the CS chain radical to produce CS‐ co ‐PAA copolymer, in addition to the PAA homopolymer 28. Furthermore, when the extent of polymerization reached a certain level, polyelectrolyte complex would be formed between positively charged CS and negatively charged PAA chains.…”

“…One has a terminal carbonyl group and the other has a free radical at the scission end. 27,28 It is thus expected that if KPS was used to initiate the polymerization in the present system, it could also degrade CS and thus produce CS chain radical. Subsequently, AA was able to grow on the CS chain radical to produce CS-co-PAA copolymer, in addition to the PAA homopolymer.…”

“…Subsequently, AA was able to grow on the CS chain radical to produce CS-co-PAA copolymer, in addition to the PAA homopolymer. 28 Furthermore, when the extent of polymerization reached a certain level, polyelectrolyte complex would be formed between positively charged CS and negatively charged PAA chains. It was observed that at the early stage of polymerization, the reaction solution was still clear.…”

“…The chemical bonding of AA unit on the degraded CS chain radical during polymerization is therefore believed to be the reason for the findings in the NMR spectra, in agreement with the previous studies. 27,28 In other words, CS-co-PAA copolymer and PAA homopolymer were both produced during the reaction, if KPS was used as the initiator.…”