Multifunctional Curcumin-Containing Segmented Polyurethanes Based on Uniform-Sized Hard Segments: Enhanced Mechanical Strength, Antioxidant Activity, and Antibacterial Functionality

Curcumin (Cur) is a reactive polyphenol with inherent antioxidant and antibacterial activities and is therefore an attractive multifunctional component for segmented polyurethanes. In this study, segmented polyurethanes (Cur-PUs) with uniform-sized hard segments were synthesized using poly(ε-caprolactone) (PCL) diol, an NCO-terminated HDI–BDO–HDI (HBH) precursor, and increasing Cur feed fractions (0–8.7 wt%). The resulting polymers were processed into films by solvent casting. 1H NMR and ATR-FTIR analyses supported urethane formation and revealed Cur-associated structural features in the isolated polymers. Across the formulation series, tensile strength increased from 13.4 to 27.5 MPa, whereas elongation at break decreased from 584.7% to 446.3%. The water contact angle increased from 67.5° to 89.0°, while equilibrium water uptake and six-month hydrolytic mass loss decreased. The Cur-containing films exhibited characteristic fluorescence, while their ethanolic extracts showed DPPH radical-scavenging activities of 67.0–91.8%. The films also produced inhibition zones of 21.0–35.0 mm against Escherichia coli; no detectable inhibition zones were observed against Staphylococcus aureus under the conditions tested. Overall, the present formulation strategy combines a structurally defined HBH-derived hard-segment precursor with Cur incorporation to obtain segmented PU films exhibiting increased tensile strength and composition-dependent functional responses under the conditions investigated.