Optical plastics have been the priority area of research for material scientists worldwide, mainly, to find alternative materials to glass, a conceptual optical material in use over the years. There are numerous advantages of using plastics for optical applications, in particular for ophthalmic applications over glass. Recently, the researchers have been putting their efforts to develop novel plastic materials to meet requirements of ophthalmic industries. The present review compiles the recent developments in the area of optical plastics. The aim is to present the current state-of-the-art in the field, besides analyzing the various aspects of developing optical plastics. The review presents various possible approaches to achieve the desired properties e.g. high refractive index of the optical plastic materials.

Plastics produced from the sulfur-based monomer are excellent materials with many optical applications such as ophthalmic lenses, fiber optics and non- linear optics. High refractive index plastic materials are able to reduce the curvature, edge and center thickness of lenses. Sulfur containing plastics such as sulfide, polysulfide, and sulfur containing vinyl compound, thioacrylate, polythiol and isocyanate/isothiocyanate based monomers have demonstrated high refractive index, high Abbe number, good impact strength, excellent machinability, good tintability and good transmittance. In the present article, various sulfur containing plastics with different types of monomers for ophthalmic lens applications are reviewed.

Refrigeration is a process to transfer heat from the objects for cooling and freezing for maintaining the temperature of surroundings for preservation purposes and comfort. Refrigerants are the materials to use in air-conditioning and refrigeration system. This article describes the developments and history of the first-, second-, third-and fourth-generation refrigerants. Moreover, the focus is on a fourth-generation refrigerant, viz. HFO-1234yf having zero ozone depletion potential and very low global warming potential. Synthesis procedure, chemistry, applications and consumption norms of HFO-1234yf are explained.

Abstract:Plastics are being preferred in almost all possible applications of materials. Several new applications including optical devices are being developed using plastics replacing conventional materials like inorganic glass etc. For the optical applications, the most important properties of plastics essential for their desired performance include refractive index, Abbe number, optical clarity, etc. The biggest challenge in developing suitable materials for optical applications has always been to meet the criteria of high refractive index along with a high Abbe number. Normally, if the refractive index increases, the Abbe number automatically decreases. The researchers have tried several approaches to deal with this typical challenge without which it is not possible to develop novel optical plastics. Presently the most popularly known optical plastics includes polymers such as polymethacrylates, polyurethanes, polycarbonates, polystyrene and diethylene glycol bis allyl carbonate. The latest material of high refractive index plastics with a refractive index of 1.67 belongs to the polythiourethanes chemistry. Several approaches are being tried world over, to develop materials of high refractive index. One of the approaches being pursued for enhancement of refractive index of existing monomers pertain to the incorporation of metals or metal salts in the matrices. The other commonly tried but difficult to achieve approaches pertain to the preparation of nanoparticles or nanocomposites.