Mechanochemically Promoted Functionalization of Postconsumer Poly(Methyl Methacrylate) and Poly(α-Methylstyrene) for Bulk Depolymerization.

We describe a methodology of post-polymerization functionalization to enable subsequent bulk depolymerization to monomer by utilizing mechanochemical macro-radical generation. By harnessing ultrasonic chain-scission in the presence of N-hydroxyphthalimide methacrylate (PhthMA), we successfully chain-end functionalize polymers to promote subsequent depolymerization in bulk, achieving up to 81% depolymerization of poly(methyl methacrylate) (PMMA) and poly(α-methylstyrene) (PAMS) within 30 min. This method of depolymerization yields a high-purity monomer that can be repolymerized. Moreover, as compared to the most common methods of depolymerization, this work is most efficient with ultra-high molecular weight (UHMW) polymers, establishing a method with the potential to address highly persistent, non-degradable all-carbon backbone plastic materials. Lastly, we demonstrate the expansion of this depolymerization method to commercial cell cast PMMA, achieving high degrees of depolymerization from post-consumer waste. This work is the first demonstration of applying PhthMA-promoted depolymerization strategies in homopolymer PMMA and PAMS prepared by conventional polymerization methods.

Selective Electrochemical Modification and Degradation of Polymers.

We demonstrate that electrochemical-induced decarboxylation enables reliable post-polymerization modification and degradation of polymers. Polymers containing N-(acryloxy)phthalimides were subjected to electrochemical decarboxylation under mild conditions, which led to the formation of transient alkyl radicals. By installing these redox-active units, we systematically modified the pendent groups and chain ends of polyacrylates. This approach enabled the production of poly(ethylene-co-methyl acrylate) and poly(propylene-co-methyl acrylate) copolymers, which are difficult to synthesize by direct polymerization. Spectroscopic and chromatographic techniques reveal these transformations are near-quantitative on several polymer systems. Electrochemical decarboxylation also enables the degradation of all-methacrylate poly(N-(methacryloxy)phthalimide-co-methyl methacrylate) copolymers with a degradation efficiency of >95 %. Chain cleavage is achieved through the decarboxylation of the N-hydroxyphthalimide ester and subsequent ß-scission of the backbone radical. Electrochemistry is thus shown to be a powerful tool in selective polymer transformations and controlled macromolecular degradation.

Bulk Depolymerization of Methacrylate Polymers via Pendent Group Activation.

In this study, we present an efficient approach for the depolymerization of poly(methyl methacrylate) (PMMA) copolymers synthesized via conventional radical polymerization. By incorporating low mol % phthalimide ester-containing monomers during the polymerization process, colorless and transparent polymers closely resembling unfunctionalized PMMA are obtained, which can achieve >95% reversion to methyl methacrylate (MMA). Notably, our catalyst-free bulk depolymerization method exhibits exceptional efficiency, even for high-molecular-weight polymers, including ultrahigh-molecular-weight (106-107 g/mol) PMMA, where near-quantitative depolymerization is achieved. Moreover, this approach yields polymer byproducts of significantly lower molecular weight, distinguishing it from bulk depolymerization methods initiated from chain ends. Furthermore, we extend our investigation to polymethacrylate networks, demonstrating high extents of depolymerization. This innovative depolymerization strategy offers promising opportunities for the development of sustainable polymethacrylate materials, holding great potential for various applications in polymer science.

Excitation Dependence in Photoiniferter Polymerization.

We report on a fundamental feature of photoiniferter polymerizations mediated with trithiocarbonates and xanthates. The polymerizations were found to be highly dependent on the activated electronic excitation of the iniferter. Enhanced rates of polymerization and greater control over molecular weights were observed for trithiocarbonate- and xanthate-mediated photoiniferter polymerizations when the n → π* transition of the iniferter was targeted compared to the polymerizations activating the π → π* transition. The disparities in rates of polymerization were attributed to the increased rate of C-S photolysis which was confirmed using model trapping studies. This study provides valuable insight into the role of electronic excitations in photoiniferter polymerization and provides guidance when selecting irradiation conditions for applications where light sensitivity is important.

Backbone Degradation of Polymethacrylates via Metal-Free Ambient-Temperature Photoinduced Single-Electron Transfer.

Polymeric materials comprised of all-carbon backbones are ubiquitous to modern society due to their low cost, impressive robustness, and unparalleled physical properties. It is well-known that these materials often persist long beyond their intended usage lifetime, resulting in environmental accumulation of plastic waste. A substantial barrier to the breakdown of these polymers is the relative chemical inertness of carbon-carbon bonds within their backbone. Herein, we describe a photocatalytic strategy for cleaving carbon-based polymer backbones. Inclusion of a low mole percent of a redox-active comonomer allows for a dramatic reduction in polymer molecular weight upon exposure to light. The N-(acyloxy)phthalimide comonomer, upon reception of an electron from a single-electron transfer (SET) donor, undergoes decarboxylation to yield a backbone-centered radical. Depending on the nature of this backbone radical, as well as the substitution on neighboring monomer repeat units, a ß-scission pathway is thermodynamically favored, resulting in backbone cleavage. In this way, polymers with an all-carbon backbone may be degraded at ambient temperature under metal-free conditions.

Novel biomechanical injury risk score demonstrates correlation with lower limb posterior chain injury in 50 elite-level rugby union athletes.

OBJECTIVES: Lower limb posterior chain injury (PCI) is common among athletic populations, with multifactorial risk factors including age, previous injury, strength measurements, range of motion and training load. Biomechanics are commonly considered in the prevention and rehabilitation of PCI by performance staff. However, there is no documented testing method to assess for associations between biomechanics and PCI. The aim of this study was to investigate whether there is an association between an easily applicable, novel biomechanical assessment tool and PCI. METHODS: Fifty male elite-level rugby union athletes (age 22.83±5.08) participating in the highest tier of England were tested at the start of the 2019 preseason period and PCIs (N=48) were recorded over the 2019/2020 playing season. Participants' biomechanics were analysed using two-dimensional video analysis against an injury risk score (IRS) system in the performance of the combined movement-prone hip extension and knee flexion. Participants' biomechanics in carrying out this movement were scored against the 10-point IRS, where the more compensatory movement recorded sees an increase in an individual's IRS. Participants' IRS was then compared against the number of PCIs sustained and Spearman's correlation coefficient was used for statistical analysis. RESULTS: There is a significant association between IRS and PCI (R=0.542, p<0.001). Linear regression demonstrated that an increase in 1 in IRS was associated with a 35% increase in PCI incidence (R²=0.346). CONCLUSION: A significance between the IRS and PCI provides preliminary support for its use as an injury risk assessment tool.

Functional and patient-reported changes in swallowing and voice after combined chemotherapy and radiotherapy for limited-stage small-cell lung cancer.

INTRODUCTION: The purpose of this study was to describe the nature and impact of dysphagia and dysphonia in patients with limited-stage small-cell lung cancer (SCLC) before and after chemoradiation. METHODS: A prospective cohort study was conducted on patients receiving chemoradiotherapy for limited-stage SCLC. Patients received either 40, 45 or 50 Gy, commencing the second cycle of chemotherapy. Outcomes included: videofluoroscopy (VFSS) to investigate aspiration, swallowing function and oesophageal motility; oral intake limitations; patient-reported dysphagia; and patient-reported dysphonia. Data were collected before treatment and one, three and six months post-treatment. RESULTS: Twelve patients were enrolled. Oropharyngeal swallowing was safe and functional at all times. Three patients exhibited oesophageal motility disorders before treatment, and a further three post-treatment. Oral intake was most compromised one month post-treatment with five patients either tube dependent or eating very limited diets. At all other times patients were eating normal or near-normal diets. Despite normal oropharyngeal swallowing on VFSS, three patients reported moderate or severe dysphagia one month post-treatment. Three additional patients reported moderate or severe difficulties three and six months post-treatment. Patients who reported dysphagia one month post-treatment all received a mean and maximum oesophageal dose of ≥15.7 Gy and ≥42 Gy, respectively. Dose-response relationships were not apparent three and six months post-treatment. Voice problems varied, with worst scores reported one month post-treatment. CONCLUSIONS: This study identified discordance between observed swallowing function and patient-reported problems, which has clinical implications for patient management, and highlights future research needs. Ongoing efforts to reduce mucosal toxicity in patients with lung cancer are essential.

Introduction of a speech-language pathology assistant role for swallow screening in a head and neck radiotherapy clinic.

PURPOSE: Optimal care suggests that all moderate-high risk head and neck (H&N) cancer patients should receive speech pathology assessment, education and management when commencing radiotherapy. However this is not always feasible due to high patient numbers and limited staffing. The aim of this study was to investigate the implementation of a speech-language pathology assistant (SLP-A) role for swallowing screening and education in a multidisciplinary H&N treatment clinic. METHOD: A detailed model of care and training module were developed to up-skill the SLP-A in the screening and education to be undertaken. A pre-test post-test design compared outcomes in two separate groups prior to and following SLP-A role implementation. Outcomes included: optimal care compliance, speech-language pathology time spent with complex patients, swallowing-related admissions and patient satisfaction. RESULT: Twenty-six patients were included pre-implementation and 35 post-implementation, with 16 (46%) patients receiving SLP-A screening/education post-implementation. The proportion of eligible patients seen by speech-language pathology pre-implementation was 62%, compared to 94% seen by speech-language pathology or SLP-A post-implementation (p = 0.002). There was a (non-significant) increase in speech-language pathology time spent with complex patients post-implementation (total minutes per patient: mean 252, SD = 144 vs. 279, SD = 115). There was no increase in swallowing-related admissions, and a (non-significant) increase in patient satisfaction post-implementation, indicating no compromise to patient safety or satisfaction. CONCLUSION: Implementing a speech-language pathology assistant role for screening patients within the H&N treatment clinic allowed delivery of optimal care and increased time for speech-language pathologists to spend with complex patients, without compromising patient safety or satisfaction.

The prevalence of patient-reported dysphagia and oral complications in cancer patients.

PURPOSE: Research investigating swallowing problems (dysphagia) and complications within the oral cavity in non-head and neck cancer patients is limited. The purpose of this study was to determine the prevalence of patient-reported dysphagia and oral complications in all cancer patients and to examine the relationships between cancer types, oral complications and dysphagia. METHODS: A cross-sectional study was conducted at a specialist cancer centre in Australia. Data on patient-reported dysphagia and oral complications were collected using the Vanderbilt Head and Neck Symptom Survey (version 2.0) which was completed by participants in one of three settings: inpatients, ambulatory patients receiving chemotherapy, or ambulatory patients receiving radiotherapy. RESULTS: Data were collected on 239 patients, receiving treatment for 14 cancer types. The proportion of patients who reported dysphagic symptoms were as follows: any dysphagia (54%); dysphagia for liquids (20%); and dysphagia for solids (46%). Significantly more head and neck patients and significantly fewer breast patients reported dysphagia, but there were no differences between other tumour types. Oral symptoms across all cancer types were reported at the following rates: taste changes (62%); xerostomia (56%); voice changes (37%); smell changes (35%); thick mucous (33%); difficulty with teeth/dentures (25%); mouth/throat pain (20%); and trismus (19%). CONCLUSIONS: This is the first time comprehensive data on dysphagia and oral complications across all cancer patients have been collected. We have identified that dysphagic symptoms and oral complications-which have implications for quality of life and function-are common in all cancer patients, not just those with head and neck cancer.