Dihydroxypropyl Chitosan: A Biorenewable Platform for the Design of Novel Fabric Care Additives

Abstract

The design of more sustainable and eco-friendly solutions is one of the central challenges in the formulation of today's laundry products. Water-soluble polymers are indispensable additives in laundry detergents as they play a wide range of functions. At present, the vast majority of these are still produced from petrochemical resources. In order to explore more sustainable alternatives, in this work, we have synthesized, characterized, and tested a novel group of anti-redeposition and soil release polymers based on hydrophobically modified 2, 3-dihydroxypropyl chitosan (DHPCH), a highly water-soluble chitosan derivative. Chitosan was selected on the basis of its environmental profile. Our results suggest that hydrophobic moieties are essential to observe cleaning benefits on synthetic based-textile. The level of modifications and the molecular weight of the unmodified chitosan were also shown to be decisive in conveying observable cleaning properties. This work is significant because it illustrates that DHPCH is a valid biorenewable platform for the development of new sustainable polymers for laundry detergents.

Scheme 1. Synthesis of (A) Dihydroxypropyl Chitosan (DC-50) and (B) Hydrophobic Modified DHPCH

Figure 1

FTIR spectra of (a) unmodified chitosan and (b) dihydroxypropyl chitosan (DC-50).

Figure 2

(a) ¹H gated-decoupling ¹³C NMR spectrum (700 MHz, D₂O) of dihydroxypropyl chitosan (DC-50), and (b) ¹³C NMR spectrum (700 MHz, D₂O) of unmodified 50 kDa chitosan.

Figure 3

¹H NMR spectra (700 MHz, D₂O) of (a) dihydroxypropyl chitosan (DC-50) and (b) unmodified chitosan.

Figure 4

¹H NMR spectra (700 MHz, D₂O) of (a) hydrophobic modified dihydroxypropyl chitosan (DC-50-B1h) and (b) dihydroxypropyl chitosan (DC-50).

Figure 5

(A) Test 1 results: WI variation (ΔWI) of PE tracers washed with a laundry detergent formulation in the presence of DHPCH derivatives (DC-50-B1h, DC-50-B1l, DC-50-O1h, and DC-50-O1l). (B) Test 2 results: ΔWI of PE tracers washed with a laundry detergent formulation in the presence of DHPCH derivatives (DC-50-B2h, DC-50-B2m, and DC-50-B2l). (C) Test 3 results: ΔWI of PE tracers washed with a laundry detergent formulation in the presence of DHPCH derivatives (DC-150-B3l, DC-150-B3h, and DC-700-B3l, and DC-700-B3h).

Figure 6

A) SRI evaluated via image analysis for PE fabrics pretreated with pure DHPCH and hydrophobic modified DHPCH (DC-50-B2l and DC-50-B2h). (B) SRI evaluated gravimetrically for PE fabrics pretreated with pure DHPCH and hydrophobic modified DHPCH (DC-50-B2l and DC-50-B2h).