High modulus hydrogels for ophthalmic and related biomedical applications

This paper presents three families of semi‐interpenetrating polymer network (SIPN) hydrogels based on an ester‐based polyurethane (EBPU) and hydrophilic monomers: N,N‐dimethylacrylamide (NNDMA), N‐vinyl pyrrolidone (NVP) and acryloylmorpholine (AMO) as potential materials for keratoprosthesis, orthokeratology and mini‐scleral lens application. Hydrogels sheets were synthesized via free‐radical polymerization with methods developed in‐house. SIPN hydrogels were characterized for their equilibrium water content, mechanical and surface properties. Three families of optically clear SIPN‐based hydrogels have been synthesized in the presence of water with >10% of composition attributable to EBPU. Water contents of SIPN materials ranged from 30% to 70%. SIPNs with ≤15% EBPU of total composition showed little influence to mechanical properties, whereas >15% EBPU contributed significantly to an increase in material stiffness. In the hydrated state, SIPNs with ≤15% EBPU of total composition show little difference in polar component (γp) of surface free energy, whereas for >15% EBPU there is a decrease in γp. The EBPU SIPN hydrogels display complementary material properties for keratoprosthesis, orthokeratology, and mini‐scleral applications

The Role of Backbone Hydration of Poly(N-isopropyl acrylamide) Across the Volume Phase Transition Compared to its Monomer

Abstract Thermo-responsive polymers undergo a reversible coil-to-globule transition in water after which the chains collapse and aggregate into bigger globules when passing to above its lower critical solution temperature (LCST). The hydrogen bonding with the amide groups in the side chains has to be contrasted with the hydration interaction of the hydrophobic main-chain hydrocarbons. In the present investigation we study molecular changes in the polymer poly(N-isopropyl acrylamide) (PNIPAM) and in its monomer N-isopropyl acrylamide (NIPAM) in solution across the LCST transition. Employing Fourier-transform infrared spectroscopy we probe changes in conformation and hydrogen bonding. We observe a nearly discontinuous shift of the peak frequencies and areas of vibrational bands across the LCST transition for PNIPAM whereas NIPAM exhibits a continuous linear change with temperature. This supports the crucial role of the polymer backbone with respect to hydration changes in the amide group in combination with cooperative interactions of bound water along the backbone chain

Oil Vulnerability Index, Impact on Arctic Bird Populations (Proposing a Method for Calculating an Oil Vulnerability Index for the Arctic Seabirds)

In recent decades, political and commercial interest in the Arctic’s resources has increased dramatically. With the projected increase in shipping activity and hydrocarbon extraction, there is an increased risk to marine habitats and organisms. This comes with concomitant threats to the fragile Arctic environment especially from oil, whether from shipping accidents, pipeline leaks, or sub-surface well blowouts. Seabirds are among the most threatened group of birds, and the main threats to these species at-sea are commercial fishing and pollution. Seabirds are vulnerable to oil pollution, which can result in mass mortality events. Species are affected to a differing extent, therefore it is important to objectively predict which species are most at risk from oil spills and where. Assessing the vulnerability of seabirds to oil is achieved through establishing an index for the sensitivity of seabirds to oil – Oil Vulnerability Index (OVI). This incorporates spatial information on the distribution and density of birds as well as on species specific behaviours and other life history characteristics. This chapter focuses on the threat of oil to seabirds, especially in the Arctic, and how an OVI can be used to highlight which species are most at risk and where within the Arctic region.© Springer Nature Switzerland AG 2020. The attached file is the final accepted manuscript version

Fabrication methods of sustainable hydrogels

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