Photopolymerization of Gels: Curing Kinetics and Degree of Conversion as Predictors of Biocompatibility

Citation: Spizhova Y., "Photopolymerization of Gels: Curing Kinetics and Degree of Conversion as Predictors of Biocompatibility", Universal Library of Medical and Health Sciences, Volume 04, Issue 01.

Copyright: This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Within the scope of the study, an in-depth analysis was conducted of the physicochemical regularities governing the photopolymerization of methacrylate systems used in contemporary nail-service practice, with particular emphasis on identifying cause-and-effect relationships between the degree of chemical conversion and the biological safety parameters of the resulting coatings. The key aspects of radical polymerization are presented in a consistent sequence, and it is shown how the spectral characteristics of current LED sources determine initiation efficiency and the ultimate curing depth of the material. Reaction completeness control is described through analytical approaches based on infrared spectroscopy (FTIR), which enables quantitative assessment of the reduction in the fraction of reactive groups and, by doing so, objectifies the degree of conversion. A separate semantic emphasis is placed on the migration of residual low-molecular-weight components, primarily 2-hydroxyethyl methacrylate (HEMA), as a critical factor shaping the toxicological profile. In parallel, the regulatory shifts of 2025 are considered, including the ban on the photoinitiator TPO within the Omnibus VII package, which necessitates revision of traditional solutions in the area of photoinitiation and formulation design. As a result of the analysis, it is demonstrated that achieving a degree of conversion above 75–80% functions as a principled condition for lowering the likelihood of allergic contact dermatitis and reducing the risk of systemic sensitization, because insufficient conversion correlates with an increased fraction of migratory monomers and oligomeric fragments. The formulated conclusions support the advisability of transitioning to updated initiation systems and substantiate the introduction of hybrid organic–inorganic materials as a technological direction capable of simultaneously increasing curing efficiency and stabilizing the composition after polymerization. The materials presented have applied significance for nail-service practice, dermatological assessment, cosmetic formulation development, and certification-oriented evaluation procedures aimed at improving safety levels within the beauty industry.

Keywords: Photopolymerization, Degree of Conversion, Methacrylates, Biocompatibility, Nail Industry, Residual Monomer, IR Spectroscopy, Photoinitiators, Omnibus VII, Allergic Contact Dermatitis.

https://doi.org/10.70315/uloap.ulmhs.2026.0401005