Synthesis of polyurethanes with pendant azide groups attached on the soft segments and the surface modification with mPEG by click chemistry for antifouling applications

Abstract

Polyurethane with pendant azide groups on the soft segment (PU-GAP) was prepared in this study to further increase the content of reactive azide groups and improve their surfaces enrichment for further functionalization. Polymer diols with pendant azide groups (GAP) were prepared by transforming the pendant chlorine groups at polyepichlorohydrin (PECH) into azide groups with sodium azide. The prepared PECH, GAP and PU-GAP was characterized by GPC, ¹H NMR and FTIR. Propargylic mPEG (mPEG-alkyne) was used as model surface modification reagents which was grafted on the prepared azido containing polyurethane films via click chemistry. The surface morphology, chemical composition and wettabilities were studied by SEM, XPS and water contact angle (WCA) analysis, respectively. SEM results demonstrated different surface topologies between mPEG modified PU surface and original PU surface. XPS and WCA analysis proved the successful grafting of mPEG on the pendant azide groups of PUs. The mPEG modified PU surfaces demonstrated good antifouling activities against model bacteria and mPEG with larger molecular weights modified surfaces showed better resistance efficiency to attachment of bacteria. Therefore, the surface reactive polyurethane we prepared can be a universal platform for further functionalization according actual applications.

Scheme 1. Schematic illustration of structure of the PU-GAP and the surface modification process of PU-GAP film (1.0 cm × 1.0 cm) with mPEG-alkyne by click chemistry for antifouling applications.

Fig. 1. Representative gel permeation chromatography (GPC) profiles of PECH, GAP and PU-GAP. The shortened retention time is characteristic for a successful increased molecular weight.

Fig. 2. FTIR spectra of PECH and GAP.

Fig. 3. The ¹H NMR spectra of PECH and GAP.

Fig. 4. XPS spectra of the PU-GAP, PU-GAP-1000, PU-GAP-3350, PU-GAP-5000 membranes.

Fig. 5. SEM microphotos of the surface morphology of unmodified and modified PU membranes.

Fig. 6. Water contact angle of PU-GAP, PU-GAP-1000, PU-GAP-3350 and PU-GAP-5000. (A) The water contact angle of the different PU films as a function of time. (B) Water contact image with different state of water drop in films.

Fig. 7. Digital images of S. aureus and E. coli colonies on agar plates after 8 h incubation corresponding to the blank control and the original, PU-GAP-1000, PU-GAP-3350 and PU-GAP-5000 films.

Fig. 8. Antifouling activities of PU, PU-GAP, PU-GAP-1000, PU-GAP-3350, PU-GAP-5000 against S. aureus (A) and E. coli (B) after 8 h incubation. Statistically significant difference were marked with asterisks (*P < 0.005, **P < 0.05, ***P < 0.5).

Fig. 9. Confocal microscopy images for different films after 8 h incubation with E. coli and S. aureus. Both the two strain cells were stained using LIVE/DEAD Baclight Bacterial Viability Kits. Size of the scale bars: 50 μm.