Multifunctional Biopolymer Nanocapsules for Antimicrobial, Fragrance-Releasing, and UV-Activated Coatings

Abstract

Multifunctional biopolymer nanocapsule coatings with antimicrobial, fragrance-releasing, and UV-activated properties were developed using poly-(eugenol methacrylate) (PEuMA) synthesized via miniemulsion polymerization. Linalool, a model essential oil, was encapsulated within the nanocapsules, while a polymerizable surfactant, P-(QAC₁₂-BP)-I, was incorporated to introduce both antimicrobial quaternary ammonium (QAC₁₂) groups and UV-reactive benzophenone (BP) moieties. The resulting spherical nanocapsules (∼400 nm) exhibited high colloidal stability (+80 mV) and achieved 70% monomer conversion within 8 h. Upon UV irradiation, the BP groups enabled covalent cross-linking between nanocapsules and cotton fabrics, significantly enhancing coating durability. The coated fabrics showed 100% bacterial reduction against and and retained 72% of the coating after 10 washing cycles. Linalool was gradually released over 7 weeks, achieving 60% cumulative release, ensuring prolonged aroma delivery. These UV-cross-linkable PEuMA nanocapsules present a robust and sustainable platform for durable antimicrobial and functional surface coatings.

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Steglich esterification reaction for the preparation of EuMA biobased monomer.

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(A) FTIR spectra of (I) QAC₁₂, (II) DMAEMA, and (III) BDC, highlighting the characteristic absorption bands: CH₂ and CH₃ stretching at 2839–2966 cm^–1, C = O stretching at 1718 cm^–1, C = C stretching at 1636 cm^–1, C–N stretching at 1295 cm^–1, C–O stretching at 1158 cm^–1, and = C–H bending at 813 cm^–1. (B) ¹H NMR spectrum of the QAC₁₂ monomer in CDCl₃, with chemical shifts (δ, ppm): 6.12 (1H, a), 5.67 (1H, b), 1.95 (3H, c), 4.65 (2H, d), 4.14 (2H, e), 3.45 (6H, f), 3.56 (2H, g), 1.78 (3H, h), 1.25–1.36 (18H, i), and 0.88 (3H, j).

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(A) FTIR spectra of (I) P­(QAC₁₂–BP)-I, (II) BP, and (III) QAC₁₂, highlighting the characteristic absorption bands: CH₂ and CH₃ stretching at 2841–2959 cm^–1, C = O stretching at 1719 cm^–1, C = C stretching at 1623 cm^–1, C–O stretching at 1148 cm^–1, and the benzene ring vibration at 701 cm^–1. (B) ¹H NMR spectrum of P­(QAC₁₂–BP)-I in CDCl₃, showing chemical shifts (δ, ppm): 1.89 (2H, a’ and d), 2.14 (3H, c), 4.58 (2H, d), 4.10 (2H, e), 3.49 (6H, f), 3.58 (2H, g), 1.76 (3H, h), 1.21–1.31 (18H, i), 0.86 (s, 3H, j), and 7.45–7.64 (8H, k).

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¹H NMR spectra of eugenol (a) and EuMA (b) biobased monomer.

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DLS histograms (a–d) and TEM images (a’–d’) of PEuMA biopolymer nanoparticles synthesized using P­(QAC₁₂–BP)-I at 0.5 wt % (a, a’, c, c’) and 1.0 wt % (b, b’, d, d’). The polymerizable surfactant was applied in the oil phase (a, a’, b, b’) and water phase (c, c’, d, d’). In the DLS histograms, the blue solid line represents the size distribution of monomer droplets before polymerization, while the red dotted line represents the size distribution of the resulting biopolymer nanoparticles.

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DLS histograms (a, b) and TEM images (a’, b’) of PEuMA biopolymer capsules encapsulating linalool, prepared with EuMA:linalool ratios of 70:30 (a, a’) and 50:50 (b, b’). In the DLS histograms, the blue solid line indicates the initial monomer droplet size, while the red dotted line indicates the size of the resulting biopolymer nanocapsules after polymerization.

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(a) TGA thermograms of original linalool (I), pure P­(QAC₁₂–BP)-I (II), PEuMA particles (III), and biopolymer nanocapsules (IV), illustrating thermal stability and encapsulation efficiency. (b) Controlled release profile of linalool encapsulated in PEuMA biopolymer nanocapsules over 7 weeks demonstrating sustained release behavior.

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(A) XPS wide-scan spectrum and (B, C) high-resolution C_1s and N_1s spectra of PEuMA nanocapsules with embedded P­(QAC₁₂–BP) on their surfaces, confirming the presence of functional groups. (D) Stability of the biopolymer nanocapsules coated onto the fabric after multiple washing cycles, showing the percentage of remaining nanoparticles at different UV activation times: 0 (white circle), 15 (dark circle), 30 (dark square), 45 (dark triangle), and 60 (dark rhombus) min after 10 washing cycles.

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Reduction of bacterial colonies on untreated (control) and biopolymer nanocapsule-coated cotton fabrics over time. Bacterial colony counts on control fabric at 0 h (a, c) and 18 h (a, c) and on biopolymer nanocapsule-coated cotton fabric at 0 h (b, d) and 18 h (b, d). (e) Percentage reduction of bacterial colonies on untreated (control) and biopolymer nanocapsule-coated cotton fabrics, demonstrating the enhanced antibacterial effect of the coated fabric.