Molecular Engineering of Polycarbonates Derived from Polyhydroxyl Natural Products as Resourceful Materials

Utilizing renewable resources can address toxicological and environmental issues associated with commodity plastics and engineering materials. In addition, scientists can exploit the various structures and chemistries of naturally occurring feedstocks to create a myriad of polymers with unique functionalities and tunable properties. With this in mind, linear polycarbonates incorporating glucose into the main chain were synthesized by AA’/BB polymerizations of phosgene, diphosgene or triphosgene and one of four different glucose-based regioisomeric diols. Each monomer exhibited unique reactivities and produced polymers with varying thermal properties. Monomers bearing hemiacetal functionalities produced polymers with low molecular weights, (>10,000 Da), whereas the remaining monomers permitted higher molecular weights (>30,000 Da). Polymers with the carbonate linkage connected to the anomeric center of the glucose ring were more thermally sensitive, with onset decomposition temperatures (Tds) ranging from 137 to 230 °C. TGA-MS analysis revealed early degradation was due to loss of carbon dioxide and benzyl protecting groups. In addition, by modifying the monomer synthetic scheme to produce AA’A’A bis-adducts, regioregular polymers possessing high molecular weights (>100,000 Da) and elevated glass transition temperatures were obtained. Functional linear polycarbonates bearing an endocyclic alkene were formed via organocatalyzed ring-opening polymerization of a six-membered carbonate monomer synthesized from ᴅ-glucal. Using 1,5,7-triazabicyclo[4.40]dec-5-ene catalyst (1 mol %) a polymer with a molecular weight of 9900 Da and polydispersity of 1.21 was obtained, whereas a 1,8-diazabicyclo[5.4.0]undec-7-ene and 1-(3,5-bis(trifluoromethyl)phenyl)-3-cyclohexyl-2-thiourea cocatalyst system (2 mol%) afforded a polymer with a molecular weight of 5000 Da and a unimodal polydispersity of 1.20. Both catalyst systems reached full conversions in dichloromethane under argon at 30 °C in fewer than ten minutes, forming amorphous polymers with a Tg at 65 °C and Tds ca. 200 °C. Tunable three-dimensional polycarbonate networks were synthesized from quinic acid, a polyhydroxyl natural product, similarly structured to glucose. Solvent-free thiol−ene chemistry was utilized in the copolymerization of tris(alloc)quinic acid and a variety of multifunctional thiol monomers to obtain poly(thioether-co-carbonate) networks with a wide range of achievable thermomechanical properties including glass transition temperatures from −18 to +65 °C. Addition of diallyl carbonate was explored as a comonomer, which allowed for the lowering of glass transitions (38 to 65°C), without altering rubbery modulus. Control force cyclic testing demonstrated excellent shape memory; high percent recoverable strains were obtained, reaching 100% recovery during fourth and fifth cycles

Molecular Engineering of Polycarbonates Derived from Polyhydroxyl Natural Products as Resourceful Materials

Utilizing renewable resources can address toxicological and environmental issues associated with commodity plastics and engineering materials. In addition, scientists can exploit the various structures and chemistries of naturally occurring feedstocks to create a myriad of polymers with unique functionalities and tunable properties. With this in mind, linear polycarbonates incorporating glucose into the main chain were synthesized by AA’/BB polymerizations of phosgene, diphosgene or triphosgene and one of four different glucose-based regioisomeric diols. Each monomer exhibited unique reactivities and produced polymers with varying thermal properties. Monomers bearing hemiacetal functionalities produced polymers with low molecular weights, (>10,000 Da), whereas the remaining monomers permitted higher molecular weights (>30,000 Da). Polymers with the carbonate linkage connected to the anomeric center of the glucose ring were more thermally sensitive, with onset decomposition temperatures (Tds) ranging from 137 to 230 °C. TGA-MS analysis revealed early degradation was due to loss of carbon dioxide and benzyl protecting groups. In addition, by modifying the monomer synthetic scheme to produce AA’A’A bis-adducts, regioregular polymers possessing high molecular weights (>100,000 Da) and elevated glass transition temperatures were obtained. Functional linear polycarbonates bearing an endocyclic alkene were formed via organocatalyzed ring-opening polymerization of a six-membered carbonate monomer synthesized from ᴅ-glucal. Using 1,5,7-triazabicyclo[4.40]dec-5-ene catalyst (1 mol %) a polymer with a molecular weight of 9900 Da and polydispersity of 1.21 was obtained, whereas a 1,8-diazabicyclo[5.4.0]undec-7-ene and 1-(3,5-bis(trifluoromethyl)phenyl)-3-cyclohexyl-2-thiourea cocatalyst system (2 mol%) afforded a polymer with a molecular weight of 5000 Da and a unimodal polydispersity of 1.20. Both catalyst systems reached full conversions in dichloromethane under argon at 30 °C in fewer than ten minutes, forming amorphous polymers with a Tg at 65 °C and Tds ca. 200 °C. Tunable three-dimensional polycarbonate networks were synthesized from quinic acid, a polyhydroxyl natural product, similarly structured to glucose. Solvent-free thiol−ene chemistry was utilized in the copolymerization of tris(alloc)quinic acid and a variety of multifunctional thiol monomers to obtain poly(thioether-co-carbonate) networks with a wide range of achievable thermomechanical properties including glass transition temperatures from −18 to +65 °C. Addition of diallyl carbonate was explored as a comonomer, which allowed for the lowering of glass transitions (38 to 65°C), without altering rubbery modulus. Control force cyclic testing demonstrated excellent shape memory; high percent recoverable strains were obtained, reaching 100% recovery during fourth and fifth cycles

The Maker movement and its impact in the fight against COVID-19

This study is an initial attempt to document the impact of the Maker movement in addressing the spread and prevention of COVID-19. During the early stages of 2020, extreme shortages of critical items led to an unprecedented global mobilisation of grassroots, community-driven Maker projects. The first part of this study reports on efforts to document Maker projects to tackle COVID-19 between March-June 2020. It analyses the characteristics of 158 projects with respect to project type, geographical region, manufacturing technologies and type of actor involved. The second part of the study provides a more detailed perspective of the challenges that Makers faced during this period, by looking at the UK case. It adopts a digital ethnographic approach, analysing a web-seminar organised and hosted by the authors in collaboration with Make:, one of the most widespread online communities of the Maker movement. The web-seminar took the form of a panel talk and discussion with representatives from four prominent COVID-19 Maker projects in the UK. This study reports on several cross-cutting themes that emerged in the panel talk. To maximise the potential impact of the Maker movement in a crisis, the findings call for: the development of a national network of Makers in the UK that is supported by policy and governance; the creation of a centralised database to manage demand and supply of critical items in times of crisis; and advancements to management of distributed quality control. This paper helps to document the impact of the Maker movement during the COVID-19 pandemic. It also underlines the potential impact of the Maker movement in addressing future crises via the development of distributed innovation actors

Evidence-based Kernels: Fundamental Units of Behavioral Influence

This paper describes evidence-based kernels, fundamental units of behavioral influence that appear to underlie effective prevention and treatment for children, adults, and families. A kernel is a behavior–influence procedure shown through experimental analysis to affect a specific behavior and that is indivisible in the sense that removing any of its components would render it inert. Existing evidence shows that a variety of kernels can influence behavior in context, and some evidence suggests that frequent use or sufficient use of some kernels may produce longer lasting behavioral shifts. The analysis of kernels could contribute to an empirically based theory of behavioral influence, augment existing prevention or treatment efforts, facilitate the dissemination of effective prevention and treatment practices, clarify the active ingredients in existing interventions, and contribute to efficiently developing interventions that are more effective. Kernels involve one or more of the following mechanisms of behavior influence: reinforcement, altering antecedents, changing verbal relational responding, or changing physiological states directly. The paper describes 52 of these kernels, and details practical, theoretical, and research implications, including calling for a national database of kernels that influence human behavior

Beyond the Formula: Using Strategic Scaffolding to Foster Critical Thinking and Authentic Writing

Much writing instruction in high school is based on using formulas and templates, such as the 5-paragraph essay. Writing these types of essays does not necessarily give students the skills and strategies they need to be successful writers beyond high school (Intersegmental Committee of the Academic Senate, 2002). Consequently, many students are graduating from high school unprepared for college and workplace writing tasks (Casner-Lotto & Barrington, 2006; Kline & Williams, 2007). In addition, formulaic writing does not necessarily foster critical thinking skills (Intersegmental Committee of the Academic Senate, 2002). Struggling students, specifically, often receive this kind of writing instruction based on templates because of the perception that they need remediation before they can compose more sophisticated texts (Brannon et al., 2008).The Beyond the Formula (BTF) curriculum was designed to provide scaffolds that foster critical thinking as a foundation for composing texts instead of requiring students to adhere to a formula. With the BTF curriculum, students analyze information from various sources about current topics and then compose texts based on rhetorical strategies, instead of using a prescribed formula. BTF was implemented in a twelfth-grade English class in a Southern California public high school. The school is designated as a Title I school. The racial demographics of the students are: 13.5% African-American, 76.7% Latino/Hispanic, 7.4% Caucasian and 1.3% Asian. The activities were designed to provide scaffolds to struggling students in order to give them access to curriculum that promoted critical thinking. In addition, the curriculum topics were based on current events in order to foster student engagement and interest.The teacher-researcher used rubrics, student interviews and essay excerpts for the evaluation. The data analysis indicates that strategic scaffolding can provide students with sufficient support to produce texts without using a formula or template. Additionally, students of all levels can participate in the prerequisite critical-thinking activities required for these kinds of writing tasks. However, struggling students need more guided instruction and practice with writing strategies and conventions to produce proficient texts. Overall, the data demonstrates that students of all levels can participate in higher-level thinking and writing activities with the support of effective scaffolds

Beyond the Formula: Using Strategic Scaffolding to Foster Critical Thinking and Authentic Writing

Much writing instruction in high school is based on using formulas and templates, such as the 5-paragraph essay. Writing these types of essays does not necessarily give students the skills and strategies they need to be successful writers beyond high school (Intersegmental Committee of the Academic Senate, 2002). Consequently, many students are graduating from high school unprepared for college and workplace writing tasks (Casner-Lotto & Barrington, 2006; Kline & Williams, 2007). In addition, formulaic writing does not necessarily foster critical thinking skills (Intersegmental Committee of the Academic Senate, 2002). Struggling students, specifically, often receive this kind of writing instruction based on templates because of the perception that they need remediation before they can compose more sophisticated texts (Brannon et al., 2008).The Beyond the Formula (BTF) curriculum was designed to provide scaffolds that foster critical thinking as a foundation for composing texts instead of requiring students to adhere to a formula. With the BTF curriculum, students analyze information from various sources about current topics and then compose texts based on rhetorical strategies, instead of using a prescribed formula. BTF was implemented in a twelfth-grade English class in a Southern California public high school. The school is designated as a Title I school. The racial demographics of the students are: 13.5% African-American, 76.7% Latino/Hispanic, 7.4% Caucasian and 1.3% Asian. The activities were designed to provide scaffolds to struggling students in order to give them access to curriculum that promoted critical thinking. In addition, the curriculum topics were based on current events in order to foster student engagement and interest.The teacher-researcher used rubrics, student interviews and essay excerpts for the evaluation. The data analysis indicates that strategic scaffolding can provide students with sufficient support to produce texts without using a formula or template. Additionally, students of all levels can participate in the prerequisite critical-thinking activities required for these kinds of writing tasks. However, struggling students need more guided instruction and practice with writing strategies and conventions to produce proficient texts. Overall, the data demonstrates that students of all levels can participate in higher-level thinking and writing activities with the support of effective scaffolds

Functional Polycarbonate of a d‑Glucal-Derived Bicyclic Carbonate via Organocatalytic Ring-Opening Polymerization

Herein, we demonstrate the synthesis of a bicyclic carbonate monomer of a d-glucal derivative, which originated from the natural product d-glucose, in an efficient three-step procedure and its ring-opening polymerization (ROP), initiated by 4-methylbenzyl alcohol, via organocatalysis. The ROP behavior was studied as a function of time, catalyst type, and catalyst concentration by using size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy. Using a cocatalyst system of 1,8-diazabicyclo[5.4.0]­undec-7-ene and 1-(3,5-bis­(trifluoromethyl)­phenyl)-3-cyclohexyl-2-thiourea (5 mol %) afforded poly­(d-glucal-carbonate) (PGCC) with almost complete monomer conversion (ca. 99%) within 1 min, as analyzed by ¹H NMR spectroscopy, and a monomodal SEC trace with dispersity of 1.13. The resulting PGCCs exhibited amorphous characteristics with a relatively high glass transition temperature at ca. 69 °C and onset decomposition temperature at ca. 190 °C, as analyzed by differential scanning calorimetry and thermogravimetric analysis, respectively. This new type of potentially degradable polymer system represents a reactive functional polymer architecture