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Alkyl Chain Length Governs Structure, Conformation and Antimicrobial Activity in Poly(alkylene biguanide)
Enas Al-Ani1, Khalid Doudin2, Andrew J McBain1
1Division of Pharmacy and Optometry, University of Manchester, Manchester M13 9PL, UK.
Polymers
|February 13, 2026
Summary
Poly(hexamethylene biguanide) (PHMB) is a versatile antimicrobial polymer. Varying its alkyl chain length impacts its antibacterial and antifungal properties, offering insights for developing new infection control agents.
Area of Science:
- Polymer Chemistry
- Antimicrobial Agents
- Biomaterials Science
Background:
- Poly(hexamethylene biguanide) (PHMB) is a broad-spectrum antimicrobial polymer used in healthcare.
- The precise relationship between PHMB's chemical structure and its antimicrobial efficacy is not fully understood.
Purpose of the Study:
- To synthesize and characterize polymeric biguanides with systematically varied alkyl chain lengths.
- To investigate how structural modifications influence physicochemical properties and antimicrobial activity.
- To elucidate structure-activity relationships for enhanced antimicrobial applications.
Main Methods:
- Synthesis and characterization using H NMR spectroscopy and FTIR.
- Solubility and dynamic light scattering measurements for physicochemical properties.
- Antimicrobial assays against Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans.
- Diffusion-ordered spectroscopy for hydrodynamic diameter and polydispersity index determination.
Main Results:
- Increasing alkyl chain length decreased aqueous solubility and increased hydrophobicity.
- Polymers with heptamethylene and octamethylene chains showed highest antibacterial activity.
- Tetramethylene- and pentamethylene-containing polymers demonstrated greater fungicidal activity.
- Excessive hydrophobicity led to aggregation and reduced antimicrobial efficacy.
Conclusions:
- Both charge density and alkyl chain length are critical determinants of antimicrobial activity in polymeric biguanides.
- Optimizing alkyl chain length is crucial for balancing antibacterial and antifungal properties.
- This study provides a foundation for designing targeted antimicrobial polymers and understanding their mechanisms of action.
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