Hybrid fluorinated copolymers containing POSS moieties along with fluorinated homopolymers were synthesized via organocatalyzed atom transfer radical (co)polymerization (O-ATRP) of fluoroalkyl methacrylate (FMA) and a POSS-based monomer (IBSS) using perylene as a photocatalyst. Linear and four- and eight-armed star-shaped (co)polymers in a wide range of molecular weights with M_n(SEC) up to 53,100 g/mol for poly(FMA), 22,700 g/mol for poly(IBSS) and 87,300 g/mol for poly(FMA-co-IBSS) were successfully prepared. During polymerization, C–F activation was found to induce chain transfer and branching reactions, contributing to structural diversity. A mechanism for chain transfer to the polymer resulting in branching was proposed, applying density functional theory (DFT). Films based on the obtained (co)polymers showed tunable morphology, high thermal stability (up to 306 °C) and hydrophobicity, with water contact angles reaching 98°.

One of the applied areas of biomechanics in ophthalmology involves studying changes in the fibrous coat of the eye in myopia. A series of studies using various methods has revealed alterations in the biomechanical properties of the sclera associated with progressive myopia due to structural and metabolic altering. However, corneal changes associated with myopia, and specifically those potentially influenced by the increase in axial length, remain less studied. Purpose. To study the biomechanical properties of the corneal stroma removed during small-incision lenticule extraction (SMILE) in myopia with varying axial length (AL). Material and methods. The study included 122 lenticules (stromal corneal fragments) obtained from patients aged 17—47 years during SMILE refractive correction for myopia. The preoperative spherical equivalent ranged from –0.75 to –13.25 D, and the AL varied between 22.64 and 29.05 mm. Baseline central corneal thickness (CCT) was 493.00—622.00 μm (mean 560.64±25.62 μm). Measurements were performed using a Bruker Bioscope Resolve atomic force microscope (Bruker, USA). Results. Selective assessment of the Young’s modulus (Y) for the anterior and posterior lenticule surfaces revealed comparable values (medians 51.00 and 53.60 kPa; minimum—maximum range 5.20—222.00 and 7.30—214.30 kPa, respectively). Analysis of the relationship between Y values and axial length showed a statistically significant but weak positive correlation for the anterior surface, in contrast to the posterior surface. A statistically significant inverse correlation was observed between Y and CCT: weak for the anterior surface and moderate for the posterior surface. Conclusion. Corneal fragments obtained during SMILE myopia correction provide a valuable model for biomechanical testing of the corneal stroma under conditions closely resembling in vivo physiology. The Young’s modulus values for the anterior and posterior lenticule surfaces were comparable and significantly correlated. The weak correlation between lenticule stiffness and axial length indirectly suggests minimal corneal biomechanical alterations associated with fibrous coat enlargement. The potential relationship between CCT and stromal biomechanics requires further investigation.

Poly(N-isopropylacrylamide) (PNIPAM)-based hydrogels are “smart” materials of great interest and demand, primarily in a variety of biomedical applications, due to their LCST close to physiological temperature. The basic biomedical applications of PNIPAM-based injectable hydrogels include controlled drug delivery, tissue engineering, wound healing, and cancer therapy. This review summarizes the thermal phase behavior of PNIPAM-based systems under different conditions, including different scenarios of physical gelation in polymer solutions and volume phase transitions in chemically crosslinked hydrogels. The thermodynamics of the coil-to-globule phase transition, its relation to gel formation, and mechanisms underlying the phase transitions in PNIPAM-based hydrogels are discussed, as well as external parameters which may affect these processes. Different types of phase diagrams observed for PNIPAM-based systems are considered, with particular attention paid to the cases in which gelation occurs separately from the coil-to-globule transition. The rational design of injectable platforms should be based upon a thorough understanding of the PNIPAM-based system’s phase behavior to achieve controllable and reproducible properties.