Controlling crosslinking in thermosets via chain transfer with monoterpenes

Biodefensive Based on Piper nigrum Essential Oil for Controlling of Anopheles aquasalis Larvae: Influence of Temperature (35 °C) and Preservatives

Considerable efforts have been spent on the development of biodefensives based on the encapsulation of essential oils for controlling of urban pests from their larval stage, especially as anopheline controlling agents. The larval source management of Anopheles aquasalis is important for malaria prevention. For this reason, this research proposes larvicidal biodefensives based on polymeric particles loaded with Piper nigrum essential oil, considering the influence of temperature (35 °C) and preservatives on the formulation stability. The biodefensive containing the preservative phenoxyethanol/methylisothiazolinone (PNE) resulted in 5 months of shelf-life storage with an Encapsulation Efficiency (EE%) of essential oil of 70%. The biodefensive PNE (containing 500 µg.mL−1 of encapsulated essential oil) presented a polydisperse particle size distribution, ranging from D10 = (127 ± 10) nm to D90 = (472 ± 78) nm and a particle mean size of (236 ± 34) nm. The AFM images revealed a spherical morphology with an external surface almost regular and smooth. The controlled release of the essential oil was evaluated up to 72 h according to the Korsmeyer-Peppas mathematical model, confirming the anomalous transport (n = 0.64 in pH = 3 and pH = 10, and n = 0.65 in pH = 7). The total larvae mortality on the in loco bioassays was almost reached (92%) after 24 h. However, according to the in vitro bioassays applying the in natura essential oil alone, the concentration of 454 μg.mL−1 resulted on the mortality of 70% of the larvae after 24 h. For this reason, the highest efficiency of the biodefensive PNE may be related to the encapsulation of essential oil, delivering the loaded particles more efficiently inside the larvae. From this perspective, the present study shows that a formulation based on P. nigrum essential oil may be taken into account in the integrated management of disease vector mosquitoes.

Sustainable Polymers: Our Evolving Understanding

ConspectusThis Account discusses the evolution of our strategy to conduct environmentally responsible research in the field of polymer chemistry. To contextualize our work, we begin with a broad historical overview of the modern environmental movement, the rise of sustainability as a concept, and how chemistry has responded to these forces, which were often sharply critical of our field. We then trace our own responses, from graduate school onward, chronicling a series of experiences and research projects that molded, challenged, and reshaped how we think about sustainability in polymer science.Since beginning our independent careers in 2004, we have recognized and worked to resolve the tension between designing synthetic polymers for specific desired thermomechanical properties and minimizing environmental impact. In our early years, we were most strongly guided by the 12 Principles of Green Chemistry (12PGC), which had only recently been proposed. The authors' early research agendas had a rather narrow focus on two areas, specifically catalysis and biobased monomers, which we saw as strongly linked to sustainability. Over time, we found these areas to be too narrow in their focus, ignoring important considerations such as the capacity of monomer supply to support scale-up and the impact polymers have at the end of their usage lifetimes. With respect to monomers and catalysts, we consider descriptive metrics that quantify waste production and the toxicity of compounds used during synthesis. In terms of polymer end-of-life, we discuss hydrophobicity as a tool to help understand susceptibility to degradation in the environment as well as some of the concerns with design for degradation, a critical component of 12PGC.Now, after nearly two decades of investigation, we believe that achieving sustainability in polymer science will require us to move beyond the qualitative use of the 12PGC to a portfolio of metrics. We note a heartening increase in the availability and use of such metrics and tools across the field. These include items that provide limited insight but are relatively trivial to integrate into existing workflows such as E factor or the Toxicity Estimation Software Tool. We also appreciate the increased use of Life Cycle Assessment (LCA), which is both dramatically more thorough and difficult to deploy. Finally, we propose the creation of a national LCA center, similar to instrumental core facilities. Such a resource would enable the use of this tool across multiple phases of research and we hope would more effectively guide us to a sustainable future.

Ranking environmental degradation trends of plastic marine debris based on physical properties and molecular structure

As plastic marine debris continues to accumulate in the oceans, many important questions surround this global dilemma. In particular, how many descriptors would be necessary to model the degradation behavior of ocean plastics or understand if degradation is possible? Here, we report a data-driven approach to elucidate degradation trends of plastic debris by linking abiotic and biotic degradation behavior in seawater with physical properties and molecular structures. The results reveal a hierarchy of predictors to quantify surface erosion as well as combinations of features, like glass transition temperature and hydrophobicity, to classify ocean plastics into fast, medium, and slow degradation categories. Furthermore, to account for weathering and environmental factors, two equations model the influence of seawater temperature and mechanical forces.

Accumulation of micro and nano-plastic in the oceans has emerged as a global challenge. Here, the authors predict a hierarchy of features that regulate their degradation and surface erosion by a thorough analysis of polymer structure, composition, physical properties and degradation data.

Manipulating the thermal and dynamic mechanical properties of polydicyclopentadiene via tuning the stiffness of the incorporated monomers

The application of polydicyclopentadiene (polyDCPD) as a high-performance thermosetting resin is often hindered by the simplicity and limitation of the polymer structure, making it unlikely to improve their thermal and dynamic mechanical properties by further optimizing the polymerization conditions. In this study, we developed a copolymer system which consisted of dicyclo-pentadienes and various designed monomers as excellent curing agents. The incorporated monomers bearing different stiffness and rigidity contain two active functional groups at the end of the structures and are capable of reinforcing original polyDCPD. The incorporated monomers notably enhanced the thermal and dynamic mechanical properties of polyDCPD. Besides that, the relationship between the stiffness of the monomer and the thermal and dynamic mechanical properties of polyDCPD was evaluated in detailed. Because of the simplicity and adjustability of copolymerization approach, optimal conditions of the copolymers with best property-reinforcing capability were systemically identified. The optimal materials displayed desired thermal and dynamic mechanical property and markedly outperformed the original polyDCPD.

Transformations of terpenes and terpenoids via carbon–carbon double bond metathesis

The review reports on transformations of unsaturated terpenes and terpenoids via olefin metathesis processes including ring closing metathesis of dienes, cross metathesis with functional olefins and ethenolysis, and ring opening metathesis as well as ring opening/cross metathesis.

Post polymer modification of polyethylenimine with citrate esters: selectivity and hydrophobicity

Hydrophobic modification of water soluble PEI with citrate esters is selective and increases log P_oct.

Cross-linked ROMP polymers based on odourless dicyclopentadiene derivatives

Hydroxydicyclopentadiene (DCPD-OH) and some ester and ether derivatives were synthesized and used for the first time as ring-opening metathesis polymerization (ROMP) monomers to create cross-linked thermoset polymers with Ru-catalysts.

Diglycerol-based polyesters: melt polymerization with hydrophobic anhydrides

The melt polymerization of diglycerol with bicyclic anhydride monomers derived from a naturally occurring monoterpene provides an avenue for polyesters with a high degree of sustainability. The hydrophobic anhydrides are synthesized at ambient temperature via a solvent-free Diels-Alder reaction of α-phellandrene with maleic anhydride. Subsequent melt polymerizations with tetra-functional diglycerol are effective under a range of [diglycerol]/[anhydride] ratios. The hydrophobicity of α-phellandrene directly impacts the swelling behavior of the resulting polyesters. The low E factors (<2), large amount of bio-based content (>75%), ambient temperature monomer synthesis, and polymer degradability represent key factors in the design of these sustainable polyesters.