Enhancement of charge-assisted hydrogen bond capabilities due to O-alkylation proximity in alkoxy cationic polythiophenes: solution- and solid-state evidence via EPR, AFM and surface free energy.

Despite the array of applications for cationic polythiophenes (CPTs), there is still a need for structure-function guidelines and mechanistic understanding of their solution- and solid-state properties. This work presents a solution- and solid-state investigation of the effect of O-alkylation proximity on the hydrogen bonding (H-bonding) capabilities of alkoxy-CPTs, based on comparing an imidazolium alkoxy CPT with strong cation-pi, pi+ and positive charge-assisted hydrogen bonding (+CAHB) capabilities (PIMa), with two isothiouronium alkoxy CPTs with two-point +CAHB capabilities (PT1 & PT2), which have short and long alkoxy side chains, respectively. Our results show that a closer proximity of O-alkylation strengthens the +CAHB capabilities of PT1: in aqueous solutions, PT2 aggregates have a stronger interaction with cationic EPR spin probes than aggregates of PIMa and PT1, which in turn show a similar extent of repulsion towards the cationic spin probes. In solid-state, atomic force microscopy (AFM) shows that PIMa generates dendritic structures onto mica, with features of diffusion-limited aggregation (DLA), indicating strong interactions with the anionic substrate due to a high configurational entropy during spreading, regardless of being drop-casted from water or 1,4-dioxane-water (W-DI), despite the latter disturbing H-bonding due to selective solvation. PT1 is also capable of generating dendritic structures resembling ballistic aggregation (BA). However, this occurs only when casting from water, since W-DI generates island-like aggregates resembling attachment limited aggregation (ALA), which is the morphology generated by PT2 regardless of the solvent. Finally, spin-coated films of PIMa and PT1 show similar dispersivity of the surface free energy (SFE), which in turn is larger than that in PT2 films, which are also more affected when casted from W-DI, presenting much larger decreases of dispersivity. These results constitute a novel empirical structure-function guideline that could be useful for optimal design and/or processing of alkoxy CPTs. For example, dendritic patterns have recently gained attention since the colloidal droplet drying is related to engineering applications including inkjet printing, biosensing, and functional material design, while the SFE is relevant for opto- and bio-electronic applications of conjugated polyelectrolytes (CPEs). This information could also be useful when analyzing previous results obtained from alkoxy CPTs with different side chain lengths.

Cationic Imidazolium Polythiophenes: Effects of Imidazolium-Methylation on Solution Concentration-Driven Aggregation and Surface Free Energy of Films Processed from Solvents with Different Polarity.

Cationic imidazolium-functionalized polythiophenes with single- or double-methylation of the imidazolium ring were used to study the impact of imidazolium-methylation on (i) the solution concentration-driven aggregation in the presence of paramagnetic probes with different ionic and hydrophobic constituents and (ii) their surface free energy (SFE) as spin-coated films deposited on plasma-activated glass. Electron paramagnetic resonance spectroscopy shows that the differences in film structuration between the polymers with different methylations originate from the early stages of aggregation. In the solid state, higher degree of imidazolium-methylation generates smaller values of total SFE, γS, (by around 2 mN/m), which could be relevant in optoelectronic applications. Methylation also causes a decrease in the polar contribution of γS (γSp), suggesting that methylation decreases the polar nature of the imidazolium ring, probably due to the blocking of its H-bonding capabilities. The values of γS obtained in the present work are similar to the values obtained for doped films of neutral conjugated polymers, such as polyaniline, poly(3-hexylthiophene), and polypyrrole. However, imidazolium-polythiophenes generate films with a larger predominance of the dispersive component of γS (γSd), probably due to the motion restriction in the ionic functionalities in a conjugated polyelectrolyte, in comparison to regular dopants. The presence of 1,4-dioxane increases γSp, especially, in the polymer with larger imidazolium-methylation (and therefore unable to interact through H-bonding), probably by a decrease of the imidazolium-glass interactions. Singly-methylated imidazolium polythiophenes have been applied as electrode selective ("buffer") interlayers in conventional and inverted organic solar cells, improving their performance. However, clear structure-function guidelines are still needed for designing high-performance polythiophene-based interlayer materials. Therefore, the information reported in this work could be useful for such applications.

Sebocyte differentiation as a new target for acne therapy: an in vivo experience.

BACKGROUND: Acne, a disease of the sebaceous gland with multifactorial pathogenesis, affects more than 85% of adolescents. A better deepening of the mechanisms underlying the disease is needed to define effective and mechanism-targeted treatments. OBJECTIVE: To understand whether the sebocyte differentiation process could be involved in the pathogenesis of the disease. METHODS: Protein expressions were evaluated by Western blot analysis and ELISA; mRNA levels by real-time RT-PCR, lipid analysis and lipid peroxidation were performed by gas chromatography, mass spectrometry and spectrophotometric assay. RESULTS: In vitro, low differentiated SZ95 sebocyte expressed an up-modulation of genes involved in sebogenesis and a higher level of insulin receptor respect to differentiated cells, resulting in an increased response to insulin and in the production of acne-like sebum. The induction of SZ95 sebocyte differentiation by the peroxisome proliferator-activated receptor γ (PPARγ) modulator NAC-GED0507 reduced the response to insulin normalizing the sebum production and decreasing the release of proinflammatory mediators. In vivo treatment of acne patients with NAC-GED0507 1% gel ameliorated clinical manifestations and induced in sebum the expression of PPARγ, associated with the decrease in mammalian target of rapamycin activation and levels of inflammatory molecules, confirming the results obtained in vitro. CONCLUSIONS: The study provides relevant insight into acne pathogenesis, identifying an alteration of sebocyte differentiation as pathogenetic basis of the disease and the induction of the differentiation process as a therapeutic target in acne therapy interfering with all pathogenic mechanisms.

Advanced Drug Delivery Nanosystems for Shikonin: A Calorimetric and Electron Paramagnetic Resonance Study.

Drug delivery is considered a mature scientific and technological platform for producing innovative medicines with nanosystems composed of intelligent bio-materials that carry active pharmaceutical ingredients forming advanced drug delivery nanosystems (aDDnSs). Shikonin and its enantiomer alkannin are natural products that have been extensively studied in vitro and in vivo for, among others, their antitumor activity, and various efforts have been made to prepare shikonin-loaded drug delivery systems. This study is focused on chimeric aDDnSs and specifically on liposomal formulations combining three lipids (egg-phosphatidylcholine; dipalmitoyl phosphatidylcholine; and distearoyl phosphatidylcholine) and a hyperbranched polymer (PFH-64-OH). Furthermore, PEGylated liposomal formulations of all samples were also prepared. Calorimetric techniques and electron paramagnetic resonance were used to explore and evaluate the interactions and stability of the liposomal formulations, showing that the presence of hyperbranched polymers promote the overall stability of the chimeric aDDnSs based on the drug release profile enhancement. Furthermore, results showed that polyethylene glycol enhances drug stabilization inside the liposomes, forming a stable and promising carrier for shikonin with improved characteristics.

Effect of Spacer Length and Solvent on the Concentration-Driven Aggregation of Cationic Hydrogen-Bonding Donor Polythiophenes.

Aggregation of cationic isothiouronium polythiophenes with alkoxy-spacers of different lengths at the 3-position of the thiophene ring was studied in solvents of different polarities. Hydrogen-bonding capacity was assessed by steady-state absorption and fluorescence spectroscopy, whereas the aggregation in aqueous solutions was studied by electron paramagnetic resonance spectroscopy, using paramagnetic probes of different polarities. The two polymers displayed similar features in respect to conformation, effect of cosolvents on aggregation, unstructured absorption-fluorescence spectra, Stokes shifts when aggregated, solvatochromic effect, and self-quenching concentration. However, these polymers also showed different specific interactions with water, Stokes shifts in water, effect of the solvent on the extent of dominant state of the S1 level, and also different inner cavities and hydrophobic-hydrophilic surface area in aqueous solution aggregates. Water maximized the difference between the polymers concerning the effect of specific increases in concentration, whereas the presence of 1,4-dioxane generated almost identical effects on both polymers.

Dendronized Anionic Gold Nanoparticles: Synthesis, Characterization, and Antiviral Activity.

Anionic carbosilane dendrons decorated with sulfonate functions and one thiol moiety at the focal point have been used to synthesize water-soluble gold nanoparticles (AuNPs) through the direct reaction of dendrons, gold precursor, and reducing agent in water, and also through a place-exchange reaction. These nanoparticles have been characterized by NMR spectroscopy, TEM, thermogravimetric analysis, X-ray photoelectron spectroscopy (XPS), UV/Vis spectroscopy, elemental analysis, and zeta-potential measurements. The interacting ability of the anionic sulfonate functions was investigated by EPR spectroscopy with copper(II) as a probe. Different structures and conformations of the AuNPs modulate the availability of sulfonate and thiol groups for complexation by copper(II). Toxicity assays of AuNPs showed that those produced through direct reaction were less toxic than those obtained by ligand exchange. Inhibition of HIV-1 infection was higher in the case of dendronized AuNPs than in dendrons.

A comparison between interactions of triglyceride oil and mineral oil with proteins and their ability to reduce cleanser surfactant-induced irritation.

OBJECTIVE: Skin irritation in personal cleansing has been correlated with surfactant binding with stratum corneum proteins. Polar and non-polar oils are increasingly being used in cleansing formulations which contain high (10-15%) level of anionic and non-ionic surfactants. However, the effects of oils in modulating skin damage from a cleansing product have not been studied in any detail. The objectives of this study are to determine whether low-viscosity polar and non-polar oils differ in their ability to reduce surfactant-induced skin irritation and, if so, how it might be related to their interactions with proteins. METHODS: Surfactant-induced skin irritation was measured by a 14-day in vivo cumulative patch irritation test. The methodology was similar to the well-known soap chamber test. Surfactant interactions with the water-soluble protein, bovine serum albumin (BSA), in the presence of oils were measured by conductometric titration. The effects of low-viscosity polar and non-polar oils on stratum corneum protein dynamics in the sulfhydryl group region were studied by electron paramagnetic resonance (EPR) using the covalently bound spin-label 3-maleimido-proxyl (5-MSL). EPR measurements were performed with stratum corneums obtained from discarded skins of 3- to 4-week-old female pigs. Simulation of the complex spectra provided insights on the environment and mobility of the protein-bound spin label. RESULTS: Addition of 1% polar sunflower seed oil (viscosity 42 centipoise) reduced in vivo irritation of 1% sodium lauryl ether sulphate with two ethoxylate/cocamidopropyl betaine (SLES/CAPB) by 20%, whereas 1% non-polar mineral oil (viscosity 15 centipoise) had no effect. Polar oil glyceryl trioleate (a major component in sunflower seed oil) at 10% level reduced surfactant binding to BSA protein in water by 40%, whereas the non-polar oil dodecane (a major component of mineral oil) at a similar level did not have any effect. The mobility of the spin label in a dry corneum was very low and was increased significantly with the addition of water and glycerol trioleate but less so with mineral oil. CONCLUSION: Sunflower seed oil reduces surfactant-induced in vivo skin irritation more than mineral oil. This is possibly due to stronger interaction of polar oil with proteins, thus protecting it from surfactant binding.

Modulation of sebum oxidation and interleukin-1α levels associates with clinical improvement of mild comedonal acne.

BACKGROUND: Sebum plays a key role in the initiation of the acne lesions. Oxidized sebum lipids cause keratynocytes hyperproliferation and inflammatory cytokines release. Association between sebum oxidation and comedogenesis has been little investigated in comedonal acne. OBJECTIVES: Evaluation of sebum oxidation parameters and levels of inflammatory cytokines (IL-1α) in patients with mild comedonal acne (MCA) before and after the treatment with a mixed RetinSphere® - vitamin E formulation. METHODS: Sebum excretion rate (SER), squalene concentration, and oxidation degree of sebum were measured in 18 MCA patients and 10 controls. IL-1α levels in the stratum corneum were measured in both lesional and non-lesional facial areas of MCA patients. Sebum parameters and IL-1α were measured at week 4 of topical treatment. Reflectance confocal microscopy (RCM) was performed in a subset of four patients at the baseline and at week 4 and all patients were assessed clinically before and following the 8 week-treatment. RESULTS: Sebum excretion rate and squalene concentration were comparable between MCA patients and healthy controls. Lipid peroxidation (LPO) and the percentage of oxidized squalene (SQOX) were significantly elevated in the sebum of MCA patients. The concentration of the proinflammatory cytokine IL-1α in stratum corneum was significantly higher in the lesional area compared with non-lesional area of the MCA patients at the baseline. At week 4, while SER and squalene concentration did not vary significantly, the LPO levels and the SQOX percentage resulted decreased at a significant extent. Following the treatment, IL-1α concentration in the lesional area reached values comparable to those of unaffected areas. Consistent with the biochemical data, RCM showed the reduction of hyperkeratinization and of inflammatory cells infiltration of the adnexal structures epithelium, significant clinical improvement was recorded at week 8. CONCLUSION: The data further support the involvement of lipid oxidation and particularly by-products of squalene oxidation in comedogenesis.

The obligation of the physician to save the life of the detainee on a hunger strike: the opinion of the Italian National Bioethics Committee.

Abstract: The Cospito case has highlighted a widely debated bioethical issue regarding the need to choose between safeguarding the life of a detainee and their right to self-determination through the practice of a hunger strike. Recently, the Italian National Bioethics Committee has been called upon to give an opinion on this matter. On the other hand, the media resonance of this case has shed light on the need to pose an ethical and social question regarding such situations: does the physician have an obligation to protect the detainee's health at the expense of their free choice? To be able to answer, it is necessary to understand whether law no. 219/17 is applicable to this context.

Consensual end-of-life for depressed patients: a right or a danger?

Abstract: Recent events have brought the debate on end-of-life issues to the forefront, particularly regarding the principle of self-determination for depressed patients. Belgian legislation, in fact, allows for requesting euthanasia when patients, capable of expressing their own will consciously, suffer in an unbearable manner and find no meaning in continuing their existence, even in the absence of incurable and/or severely debilitating conditions. The state of the art is an increasing number of people who die from euthanasia. An open question is when a situation can be defined as unbearable. Moreover, does such an assessment necessarily lead to death, or are there other solutions? In our opinion, such a practice should be limited to prevent inappropriate applications that could lead to infringing depressed patients' rights.

Obstetric Violence in Italy: From Theoretical Premises to Court Judgments.

Introduction: Historical mistreatment and violence directed toward women's bodies extend to the field of medicine, and obstetric and gynecological practices are not immune to such misconduct. Obstetric violence (OV) refers to actions involving disrespectful, abusive, or coercive treatment directed at pregnant and birthing women. This includes institutional and personal attitudes that lead to the violation of women's autonomy, human rights, and sexual and reproductive health. Despite various international legislative initiatives and recommendations from the World Health Organization (WHO) addressing disrespectful and abusive treatment, OV is still poorly known to Italian public opinion. This study aims to investigate whether the concept of OV has been conversely assimilated in judicial decisions. Materials and methods: A retrospective analysis was conducted to scrutinize judgments in Italy until June 2023 related to OV. The Italian legal database 'De Jure Giuffrè', which collects sentences by various Courts, and the terms 'obstetric' and 'violence' as keywords were used for the research. Results: The full-text revision of the results (n. 41 sentences) al-lowed the selection of 5 eligible contributions covering the following issues: Informed Consent, Kristeller maneuver, Vaginal Birth After Cesarean (VBAC), Acceleration of childbirth without indication, and Episiotomy. The analysis of individual judgments was complemented by an examination of the key issues involved. Conclusions: The reviewed judgments frequently seemed to be grounded in technical aspects and inclined towards a predominant evaluation of childbirth outcomes. However, some encouraging aspects emerged, particularly in terms of attention to the female body, acknowledgment of consequences within the intimate-relational dimension, and a commitment to the principle of self-determination through the provision of free and informed consent. Ensuring the psychophysical well-being of women and unborn children, fostering positive interactions between pregnant women and medical staff, and actively working to reduce the grounds for litigation are among actual emerging priorities in healthcare. In this sense, fundamental elements include the implementation of continuous staff training and education as well as a focus on promoting the self-determination of women, leveraging new technologies for this purpose, and ensuring legal protection of their rights.

Loss of chance: the uncertainty of the event or the uncertainty of the conduct? Case Series and Medicolegal Considerations.

Background: The concept of damages for loss of chance originated in France in 1877 and was adapted to healthcare in 1962. In Italy, it was first introduced in healthcare liability in 2004, with Civil Court of Cassation decision No. 4400. Italian jurisprudence recognizes the loss of chance as an independent, legally and economically assessable damage, distinct from the actual outcome lost. The landmark St. Martin Judgments of 2019 further established that such damages can be claimed if they involve appreciable, serious, and consistent values. This requires proving a causal link between the conduct and the lost chance, based on established civil law criteria. Case report: 1) a 71-year-old man whose lung carcinoma was not diagnosed in time, leading to a significant reduction in survival chances. 2) a woman whose breast cancer diagnosis was delayed, resulting in a more advanced stage and decreased survival prospects. Discussion: In medical professional liability, the Supreme Court requires a high probability or certainty of causation for recognizing the causal link between wrongful conduct and damage. The assessment involves proving both the causal link and the reasonable probability of a lost opportunity's realization. Hypothetical damage is insufficient for compensation. Conclusions: The compensability of loss of chance relies on proving the causal link between the negligent act and the uncertain event, where the impact on the patient's non-pecuniary sphere is significant. Medicolegal practice faces challenges in distinguishing between causality and damage, which can lead to confusion between biological damage and damage from loss of opportunity.

Heterogeneous micellar solubilization within lyotropic liquid crystals interfaces.

The solubilization of sodium diclofenac (Na-DFC) in a glycerol monooleate-based emulsion triggers series of structural changes. Incorporation of Na-DFC, leads to formation of a reverse hexagonal mesophase between 2 and 5 wt% Na-DFC. Between 6 and 9 wt% Na-DFC, the hexagonal symmetry gradually transitions to a disordered lamellar mesophase. These structural shifts impact the system's storage modulus, structuring enthalpy, and structural diffusivity. Despite these transitions, the driving force for Na-DFC release remains consistent, leading to hypothesize that the interfacial structure remains unchanged during Na-DFC release. The nano-structural modifications imposed by the Na-DFC load and release were assessed by small-angle X-ray diffraction (SAXD), spin-probe electron paramagnetic resonance (EPR), and nuclear quadrupole resonance (NQR). The selective solubilization of Na-DFC was demonstrated by SAXD peak fittings, revealing an increase of hexagonally oriented rods at the expense of non-oriented micelles, rather than gradual micellar elongation. Computation of the EPR spectra also showcased the selective solubilization of Na-DFC at an enhanced free energy interface (γ), evidenced by step-wise variations in polarity, microviscosity, and order parameters. Additionally, NQR analysis highlighted a higher anisotropy for sodium compared to deuterium, linking the selective solubilization of Na-DFC to heterogeneous structural transformations. These findings underscore the heterogeneous nature of solubilization-release processes, driven by locally increased micellar free energy. Consequently, the loaded Na-DFC interfaces maintain a constant γ, ensuring a consistent release driving force despite the structural transitions affecting the matrix. The ability to selectively solubilize guest molecules may herald a new era in the utilization of selective molecular interfacial loading.

Artificial intelligence and future perspectives in Forensic Medicine: a systematic review.

Objective: Artificial intelligence (AI) is the ability of a computer machine to display human capabilities such as reasoning, learning, planning, and creativity. Such processing technology receives the data (already prepared or collected), processes them, using models and algorithms, and answers questions about forecasting and decision-making. AI systems are also able to adapt their behavior by analyzing the effects of previous actions and working then autonomously. Artificial intelligence is already present in our lives, even if it often goes unnoticed (shopping networked, home automation, vehicles). Even in the medical field, artificial intelligence can be used to analyze large amounts of medical data and discover matches and patterns to improve diagnosis and prevention. In forensic medicine, the applications of AI are numerous and are becoming more and more valuable. Method: A systematic review was conducted, selecting the articles in one of the most widely used electronic databases (PubMed). The research was conducted using the keywords "AI forensic" and "machine learning forensic". The research process included about 2000 Articles published from 1990 to the present. Results: We have focused on the most common fields of use and have been then 6 macro-topics were identified and analyzed. Specifically, articles were analyzed concerning the application of AI in forensic pathology (main area), toxicology, radiology, Personal identification, forensic anthropology, and forensic psychiatry. Conclusion: The aim of the study is to evaluate the current applications of AI in forensic medicine for each field of use, trying to grasp future and more usable applications and underline their limitations.

Gender Gap in academic medicine: a narrative review and the Italian forensic context.

Background: Gender gap is a neologism that identifies the disparity between social and professional conditions experienced by females compared to males. The disparity increases as one ascends the academic hierarchy. In recent years, the debate has expanded, and more options have been planned for the elimination of the current gender gap. Methods: This research was conducted by examining the landscape of the gender gap, particularly in the academic forensic medicine field. Our analysis involved reviewing papers published between 2006 and 2024, identified through electronic database searches (PubMed). The search terms used were: "gender gap" AND "academic" AND "medicine" AND "leadership." In total, we analyzed 85 papers. Additionally, we examined data from forensic medicine residency programs. Conclusions: The representation of women in medicine is well-known. Despite the increasing number of women in leadership positions in medicine, they still lag significantly behind men. These data highlight a situation that could be seen as grounds for an accusation of "academic abuse". In the Italian forensic residency programs, less than 20% are led by women, and among these, not all hold the rank of full professor. Although a certain rebalancing is already underway, the gap is still significant. There are already regulations obliging local authorities to promote gender equality in councils, companies, and institutions under their jurisdiction. It would be desirable to consider minimum quotas for female participation in university competitions. This would be a first step toward eliminating the gender gap in academic and forensic medical fields.

Z-Drugs and their use in Drug-Facilitated Crimes: a review of the literature.

Background: Z-Drugs are a category of non-benzodiazepine sedative-hypnotic drugs that include Zolpidem, Zopiclone and Zaleplon. They are all rapidly adsorbed and have a very short half- life, features that make them first-line treatment of insomnia and, in the meantime, first-choice drugs in cases of poisoning for criminal purposes. Z-drugs are frequently use in Drug Facilitated Crime cases (DFC) and Drug Facilitated Sexual Assault (DFSA), namely crimes, robberies, extortion and sexual violence committed after administration of incapacitating substances able to induce sedative-hypnotic effects. In these circumstances, the psychoactive substance is considered as a weapon and constitutes an aggravating circumstance in the criminal act: accordingly, judicial authority legitimates the analytical determination of these substances. Currently, few tests able to detect such drugs are available in daily clinical practice. Aim: The aim of this work is to evaluate the effective utilization of Z-Drugs. Methods: We have analyzed the literature, focusing on cases in which the criminal use of such incapacitating substances has been demonstrated. Relevant scientific articles were identified from PubMed, Cochrane Central, Scopus, Web of Science, Science Direct, EMBASE up to December 2022 using the following keywords: "z-drugs", "drug facilitated crime", "forensic toxicology". The resulting references were screened to exclude duplicates. In addition, non-English papers were excluded. This evaluation left 10 articles (8 case reports and 2 original studies) divided as follows: 1 case report of a DFC (robbery), 6 cases of confirmed DFSA, 3 cases of suspected DFSA, 2 original studies about DFC. Results: The totality of the selected cases showed positive toxicological tests for a single intake of z-drugs. Conclusions: This work has shown the limitations of screening tests currently in use in the emergency rooms. Forensic toxicology tests should be introduced in daily clinical practice.

"Brush-first" method for the parallel synthesis of photocleavable, nitroxide-labeled poly(ethylene glycol) star polymers.

We describe the parallel, one-pot synthesis of core-photocleavable, poly(norbornene)-co-poly(ethylene glycol) (PEG) brush-arm star polymers (BASPs) via a route that combines the "graft-through" and "arm-first" methodologies for brush polymer and star polymer synthesis, respectively. In this method, ring-opening metathesis polymerization of a norbornene-PEG macromonomer generates small living brush initiators. Transfer of various amounts of this brush initiator to vials containing a photocleavable bis-norbornene cross-linker yielded a series of water-soluble BASPs with low polydispersities and molecular weights that increased geometrically as a function of the amount of bis-norbornene added. The BASP cores were cleaved upon exposure to UV light; the extent of photo-disassembly depended on the amount of cross-linker. EPR spectroscopy of nitroxide-labeled BASPs was used to probe differences between the BASP core and surface environments. We expect that BASPs will find applications as easy-to-synthesize, stimuli-responsive core-shell nanostructures.

EPR analysis and DFT computations of a series of polynitroxides.

Polynitroxides with varying numbers of nitroxide groups (one to four) derived from different aromatic core structures show intramolecular electron spin-spin coupling. The scope of this study is to establish an easy methodology for extracting structural, dynamical, and thermodynamical information from the EPR spectra of these polynitroxides which might find use as spin probes in complex systems, such as biological and host/guest systems, and as polarizing agents in dynamic nuclear polarization (DNP) applications. Density functional theory (DFT) calculations at the B3LYP/6-31G(d) level provided information on the structural details such as bond lengths and angles in the gas phase, which were compared with the single crystal X-ray diffraction data in the solid state. Polarizable continuum model (PCM) calculations were performed to account for solvent influences. The electron paramagnetic resonance (EPR) spectra of the polynitroxides in chloroform were analyzed in detail to extract information such as the percentages of different conformers, hyperfine coupling constants a, and rotational correlation times τ(c). The temperature dependence on the line shape of the EPR spectra gave thermodynamic parameters ΔH and ΔS for the conformational transitions. These parameters were found to depend on the number and relative positions of the nitroxide and other polar groups.

EPR study of spin labeled brush polymers in organic solvents.

Spin-labeled polylactide brush polymers were synthesized via ring-opening metathesis polymerization (ROMP), and nitroxide radicals were incorporated at three different locations of brush polymers: the end and the middle of the backbone, and the end of the side chains (periphery). Electron paramagnetic resonance (EPR) was used to quantitatively probe the macromolecular structure of brush polymers in dilute solutions. The peripheral spin-labels showed significantly higher mobility than the backbone labels, and in dimethylsulfoxide (DMSO), the backbone end labels were shown to be more mobile than the middle labels. Reduction of the nitroxide labels by a polymeric reductant revealed location-dependent reactivity of the nitroxide labels: peripheral nitroxides were much more reactive than the backbone nitroxides. In contrast, almost no difference was observed when a small molecule reductant was used. These results reveal that the dense side chains of brush polymers significantly reduce the interaction of the backbone region with external macromolecules, but allow free diffusion of small molecules.