Theoretical design of durable and strong polycarbonates against photodegradation

The photodegradation mechanism of polycarbonate (PC) was investigated by quantum chemistry, and a novel antidegradation molecular design using substituents was proposed. It was demonstrated that electron-withdrawing substituents in the phenyl moiety controlled bond alternation, leading to inhibition of the O-C bond cleavage in the carbonate moiety. These results provide a promising alternative for durable PC synthesis.

A review of the selection process and decontamination methods with the use of face shields in UV phototherapy during the SARS-CoV-2 pandemic

Targeted ultraviolet (UV) phototherapy has been used in the management of a wide variety of dermatological clinical conditions including moderate to severe psoriasis unresponsive to topical therapies, vitiligo, severe atopic dermatitis and lymphoproliferative disorders. To date there are no uniform, standardised guidelines for the selection and decontamination process for UV personal protective equipment (PPE) and facial shields used in phototherapy. In the current climate, Coronavirus 2019 (COVID-19) pandemic, standards regarding all decontamination and disinfection processes are under significant scrutiny. In terms of the UV-PPE and facial shields used in phototherapy, careful disinfection procedures need to be implemented to ensure that the decontamination practice is effective enough to neutralise the virulent virus whilst maintaining maximal protection to the user from UV-rays and safeguard the equipment from damage during the cleaning process. The aim of this report is to provide an evidence based review of the current and international practice standards guiding the selection, use and decontamination processes of UV facial shields in phototherapy. The complications and concerns that the COVID-19 pandemic has had on this practice is highlighted. As such, we performed a comprehensive evaluation of the literature to provide recommendations as to the most effective, time efficient and safest practices for disinfection and decontamination of UV facial shields used in phototherapy during these unprecedented times.

Theoretical Analysis of Properties of Ground and Excited States for Photodissociation of the C-O Bond in Polycarbonates

Quantum chemical calculations were carried out to investigate the properties of the ground state (GS) and the excited state (ES) of bisphenol-A polycarbonate (PC) with bisphenol-A hydrogen carbonate (BPAHC) as a model compound. Time-dependent density functional theory (TDDFT) was used to obtain the absorption spectrum and the corresponding transition natures of BPAHC. Furthermore, the ESs related to the transitions of the carbonate group and neighboring phenyl ring were optimized employing the TDDFT method for photodegradation. Our results showed that the carbonate group is broken at an ES with relatively high energy, which has a significant C-O bond cleavage within the carbonate group compared to that of GS geometry. The carbonate group C-O bond cleavage is caused by two reasons. One is the transition from the O lone pair to the carbonate π anti-bonding which is commonly known, and the other one is the transition from the O lone pair to the phenyl group (adjacent to the carbonate group) π anti-bonding that is newly proposed.

Coating-relevant properties of high-index optical polymers for automotive applications

High-transparent polymers exhibiting a refractive index beyond 1.6 enhance the available range of optical plastics. The aim of this study is to evaluate optical polyesters (OKP-1 and OKP-4) and special new polycarbonates (PCs) (EP-6000 and EP-8000) in comparison with the widely used poly-bisphenol-A-based PC. The work is focused on optical properties as well as other properties that are important for the deposition of optical coatings. Plasma ion-assisted deposition is used for the deposition of an abrasion resistant antireflective coating (AR-hard).

Theoretical study on the decomposition mechanism of bisphenol A polycarbonate induced by the combined effect of humidity and UV irradiation

Polycarbonate (PC) is a good material for covering and protecting cultural heritage sites because of its durability, mechanical properties, and transparency. When bisphenol A polycarbonate is subjected to weathering conditions this polymer shows several degradation processes depending on the irradiation wavelength, humidity and temperature. In particular, the combined effects of humidity and UV irradiation speed up the PC molecular weight reduction. In this work, the decomposition mechanisms associated to the hydrolysis process are scrutinized and the effects of UV irradiation on the hydrolysis process are evaluated throughout the Density Functional Theory (DFT) approach. It was found that under UV irradiation the hydrolysis process is speeded up because of the geometrical rearrangement due to the photo-Fries process induced by the UV light.

Chemical recycling of poly(bisphenol A carbonate)

This review covers the current status of chemical recycling and upcycling of poly(bisphenol A carbonate), a leading engineering plastic of great economic and environmental interest.

Effect of environmental conditions on the durability of polycarbonate for the protection of cultural heritage sites

Polycarbonate is a good material for covering and protecting cultural heritage sites because of its durability, mechanical properties, and transparency. However, polycarbonate degrades under environmental weathering with a significant decrease of physical and mechanical properties and loss of transparency. In this work, the contemporary presence of ultraviolet irradiation and different temperature and moisture conditions have been taken into account to study the environmental degradation of this polymer with regard to its mechanical and optical properties. The photo-oxidation reactions cause a decrease in the molecular weight and the formation of many oxygenated species. The hydrolytic scission, instead, gives rise to a remarkable reduction in the molecular weight. These two different degradation mechanisms do not seem interconnected because at the lowest degradation temperature and high humidity levels, the reduction of the molecular weight is more pronounced than that observed at the highest temperature but at a lower humidity level. Transparency decreases with the degradative processes, but even after severe degradation the loss of transparency is only about 10%. The yellowness index increases during the first stages of degradation, which has been attributed to the fast formation of carbonyl groups due to photo-oxidation.

Poly(Alkyl Glycidate Carbonate)s as Degradable Pressure-Sensitive Adhesives

Insertion of CO₂ into the polyacrylate backbone, forming poly(carbonate) analogues, provides an environmentally friendly and biocompatible alternative. The synthesis of five poly(carbonate) analogues of poly(methyl acrylate), poly(ethyl acrylate), and poly(butyl acrylate) is described. The polymers are prepared using the salen cobalt(III) complex catalyzed copolymerization of CO₂ and a derivatized oxirane. All the carbonate analogues possess higher glass-transition temperatures (T_g =32 to -5 °C) than alkyl acrylates (T_g =10 to -50 °C), however, the carbonate analogues (T_d ≈230 °C) undergo thermal decomposition at lower temperatures than their acrylate counterparts (T_d ≈380 °C). The poly(alkyl carbonates) exhibit compositional-dependent adhesivity. The poly(carbonate) analogues degrade into glycerol, alcohol, and CO₂ in a time- and pH-dependent manner with the rate of degradation accelerated at higher pH conditions, in contrast to poly(acrylate)s.

Antireflection coating with UV-protective properties for polycarbonate

Polycarbonate is the chosen material for covers of automotive displays because it combines high transparency with high breaking strength. The requirements for coatings include an improvement of the scratch resistance and antireflection properties as well as high stability for challenging environmental conditions. A coating that involves all required properties has been developed and deposited onto polycarbonate by plasma-ion assisted deposition.

Review of modern techniques to generate antireflective properties on thermoplastic polymers

Modern optical applications need solutions for providing polymer surfaces with antireflective properties. The problems involved in coating comprise thermal limitations, incompatible mechanical properties of coating and substrate materials, and interaction between polymers and plasma. As an alternative for coating, antireflective properties on polymers can also be obtained by hot embossing or by ion etching of surface structures. My objective is to provide the criteria for choosing suitable deposition or structuring methods based on an understanding of plasma-, radiation-, and ion-induced surface phenomena; material compatibility; mechanical and environmental performance; and cost issues. The potential to produce antireflective interference coatings is documented for plasma-enhanced physical- and chemical-vapor-deposition methods, including modern hybrid techniques, as well as for solgel wet-chemical processes. The review about state-of-the-art coatings focuses on the thermoplastic acrylic, polycarbonate, and cycloolefin polymers.