α-amino acid-derived polyamidoamines as photostabilizers for cotton

Arginine- (M-ARG), glycine- (M-GLY), serine‑ (M-SER), histidine- (M-HIS) and tyrosine/arginine- (M-TYR30-ARG70) derived polyamidoamines (PAAs) were studied as cotton photostabilizers. Cotton strips with a 6 wt. % PAA add-on were subjected to accelerated photoaging in a solar chamber under UVA–UVB exposure at 40 % relative humidity and 30–35 ◦C. Colorimetric analysis was conducted at 15-minute intervals during irradiation. Virgin cotton exhibited significantly more yellowing than PAA-treated fabrics, except for those treated with MTYR30-ARG70. Scanning electron microscopy revealed slight surface erosion on untreated cotton (COT) fibers after prolonged UV exposure, whereas PAA-treated cotton (COT/PAA) showed uniform PAA coatings with only minor surface wrinkles and localized fractures. Colorimetric analysis enabled ranking the photostability of COT/PAA samples as follows: COT/M-ARG > COT/M-GLY > COT/M-SER > COT/M-HIS > COT > COT/M-TYR30- ARG70. These results demonstrate that all PAAs enhanced UV protection, except for M-TYR30-ARG70. Nuclear magnetic resonance analysis of PAA coatings extracted from photoaged cotton showed no detectable structural degradation. The results confirm that α-amino acid-derived PAAs effectively protect cotton from photoaging, although formulations containing UVB-absorbing residues exhibit increased susceptibility to irradiation. The effectiveness of PAAs was attributed to the radical scavenging activity of tert‑amine groups and the side-chain residues within their repeat units.