Preparation and Stabilization of High Molecular Weight Poly (acrylonitrile-co-2-methylenesuccinamic acid) for Carbon Fiber Precursor

Bifunctional comonomer 2-methylenesuccinamic acid (MLA) was designed and synthesized to prepare acrylonitrile copolymer P (AN-co-MLA) using mixed solvent polymerization as a carbon fiber precursor. The effect of monomer feed ratios on the structure and stabilization were characterized by elemental analysis (EA), Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), X-ray diffraction (XRD), proton nuclear magnetic (1H NMR), and differential scanning calorimetry (DSC) for the P (AN-co-MLA) copolymers. The results indicated that both the conversion and molecular weight of polymerization reduce gradually when the MLA content is increased in the feed and that bifunctional comonomer MLA possesses a larger reactivity ratio than acrylonitrile (AN). P (AN-co-MLA) shows improved stabilization compared to the PAN homopolymer and poly (acrylonitrile-acrylic acid-methacrylic acid) [P (AN-AA-MA)], showing features such as lower initiation temperature, smaller cyclic activation energy, wider exothermic peak, and a larger stabilization degree, which are due to the ionic cyclization reaction initiated by MLA, confirming that the as-prepared P (AN-co-MLA) is the potential precursor for high-performance carbon fiber.

Tunable, biodegradable grafting-from glycopolypeptide bottlebrush polymers

The cellular glycocalyx and extracellular matrix are rich in glycoproteins and proteoglycans that play essential physical and biochemical roles in all life. Synthetic mimics of these natural bottlebrush polymers have wide applications in biomedicine, yet preparation has been challenged by their high grafting and glycosylation densities. Using one-pot dual-catalysis polymerization of glycan-bearing α-amino acid N-carboxyanhydrides, we report grafting-from glycopolypeptide brushes. The materials are chemically and conformationally tunable where backbone and sidechain lengths were precisely altered, grafting density modulated up to 100%, and glycan density and identity tuned by monomer feed ratios. The glycobrushes are composed entirely of sugars and amino acids, are non-toxic to cells, and are degradable by natural proteases. Inspired by native lipid-anchored proteoglycans, cholesterol-modified glycobrushes were displayed on the surface of live human cells. Our materials overcome long-standing challenges in glycobrush polymer synthesis and offer new opportunities to examine glycan presentation and multivalency from chemically defined scaffolds.

Influence of Component Ratio on Thermal and Mechanical Properties of Terpenoid-Sulfur Composites

Terpenoids are potentially sustainable replacements for petrochemical olefins. Sulfur is a waste product produced in large quantities from fossil fuel refining. Several composites with attractive properties have recently been made from terpenoids and sulfur. This report details the extent to which the ratio of sulfur to terpenoid and the terpenoid olefin content influences the thermal and mechanical properties of such terpenoid-sulfur composites. The terpenoids selected were diunsaturated geraniol and triunsaturated farnesol that, upon their inverse vulcanization with elemental sulfur, yield composites GerSx and FarSx, respectively (x = wt % sulfur). The wt % sulfur in the monomer feed was varied from 30–95 for this study, providing twelve materials. Mechanical analysis of these materials was undertaken by compressive and tensile strength techniques. Differential scanning calorimetric analysis revealed both polymeric and orthorhombic sulfur present in the materials with glass transition temperatures (Tg) of −37 °C to −13 °C and melt temperatures (Tm) of 119 to 104 °C. The crystallinity of composites decreases as the weight fraction of sulfur decreases and composites having the highest olefin content exhibit no detectable crystalline microstructures. The compressive strength of the materials showed increasing strength for higher olefin-content materials for both GerSx (with compressive strength of up to 32 MPa) and FarSx (with compressive strength of up to 43 MPa). The improved strength with increasing olefin content levels off at around 80–85% of terpenoid, after which point both tensile and compressive strength diminish.

Importance of pH in Synthesis of pH-Responsive Cationic Nano- and Microgels

While cationic microgels are potentially useful for the transfection or transformation of cells, their synthesis has certain drawbacks regarding size, polydispersity, yield, and incorporation of the cationic comonomers. In this work, a range of poly(N-isopropylacrylamide) (PNIPAM) microgels with different amounts of the primary amine N-(3-aminopropyl)methacrylamide hydrochloride (APMH) as the cationic comonomer were synthesized. Moreover, the pH-value during reaction was varied for the synthesis of microgels with 10 mol% APMH-feed. The microgels were analyzed by means of their size, thermoresponsive swelling behavior, synthesis yield, polydispersity and APMH-incorporation. The copolymerization of APMH leads to a strong decrease in size and yield of the microgels, while less than one third of the nominal APMH monomer feed is incorporated into the microgels. With an increase of the reaction pH up to 9.5, the negative effects of APMH copolymerization were significantly reduced. Above this pH, synthesis was not feasible due to aggregation. The results show that the reaction pH has a strong influence on the synthesis of pH-responsive cationic microgels and therefore it can be used to tailor the microgel properties.

Crosslinking in Semi-Batch Seeded Emulsion Polymerization: Effect of Linear and Non-Linear Monomer Feeding Rate Profiles on Gel Formation

Waterborne latex is often called a product-of-process. Here, the effect of semi-batch monomer feed rate on the kinetics and gel formation in seeded emulsion polymerization was investigated for the copolymerization of n-butyl methacrylate (n-BMA) and ethylene glycol dimethacrylate (EGDMA). Strikingly, the gel fraction was observed to be significantly influenced by monomer feed rate, even while most of the experiments were performed under so-called starve-fed conditions. More flooded conditions from faster monomer feed rates, including seeded batch reactions, counterintuitively resulted in significantly higher gel fraction. Chain transfer to polymer was intentionally suppressed here via monomer selection so as to focus mechanistic insights to relate only to the influence of a divinyl monomer, as opposed to being clouded by contributions to topology from long chain branching. Simulations revealed that the dominant influence on this phenomenon was the sensitivity of primary intramolecular cyclization to the instantaneous unreacted monomer concentration, which is directly impacted by monomer feed rate. The rate constant for cyclization for these conditions was determined to be first order and 4000 s−1, approximately 4 times that typically observed for backbiting in acrylates. This concept has been explored previously for bulk and solution polymerizations, but not for emulsified reaction environments and especially for the very low mole fraction divinyl monomer. In addition, while gel fraction could be dramatically manipulated by variations in linear monomer feed rates, it could be markedly enhanced by leveraging non-linear feed profiles built from combination sequences of flooded and starved conditions. For a 2 h total feed time, a fully linear profile resulted in 30% gel while a corresponding non-linear profile with an early fast-feed segment resulted in 80% gel.

Tailoring Nano-copolymer/CNTs Composite and Its Application in Drug Delivery

This work aimed to overcome the main drawbacks of some essential anticancer drugs as 5-Fluorouracil (5-FU) by controlled loading with novel drug carriers. By a differential microemulsion technique, nanosized particles derived from a copolymer of poly(methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA)) with different monomer ratios have been synthesized and used as a drug carrier. Poly(MMA-co-HEMA)/MWCNT nanocomposite was also synthesized using an in-situ microemulsion polymerization technique and used as a 5-FU carrier. Different techniques have characterized these ground-breaking drug delivery systems such as FT-IR, XRD, TEM, TGA, zeta potential, and a particle size analyzer. The effects of monomer feed composition, 5-FU content, and MWCNTs content on morphological and structural properties, in-vitro 5-FU release, and entrapment efficiency (EE%) have been studied. It was noted that the inclusion of MWCNTs in the 5-FU-loaded polymer increases the thermal stability and raises the entrapment efficiency (EE%) to hit 99% at CNTs:5-FU ratio of 2:1. The anticancer drug release from the co-polymeric nanospheres depends on the HEMA ratio, 5-FU/copolymer ratio, CNT/5-FU ratio, and the pH of the medium. The optimized nanocomposite demonstrated higher anti-tumor activity against the cell lines CaCo-2, MCF-7, and HepG-2 and higher cytotoxicity against HepG-2 relative to CaCo-2 and MCF-7.

Environmental Profile and Technological Validation of New High-Tg Unsaturated Polyesters from Fully Bio-Based Monomers and Reactive Diluents

This study was focused on the synthesis and characterization of a fully bio-based unsaturated polyester resin (UPR) with good thermal properties suitable for the commercial production of composite polymers. UPRs based on different ratios of bio-based furan dicarboxylic acid (FDCA), itaconic acid, and diols were synthesized. The unsaturated polymers prepared were evaluated by differential scanning calorimetry, gel permeation chromatography, FTIR and 1H-NMR spectroscopy. The results showed positive effects of FDCA on the glass transition temperature (Tg) of these fully bio-based polyesters, especially when FDCA was combined with 1,2-propanediol. Optimal values of Tg were obtained in the range of 30–32 °C for UPRs synthesized starting with a higher concentration of FDCA in the monomer feed. The possibility of substituting styrene, which usually acts as a reactive diluent, with a greener and safer alternative during the crosslinking of UPRs, was also explored. Two bio-based reactive diluents were considered: dimethyl itaconate (DMI) and butanediol dimethacrylate. After crosslinking, an average Tg of 75 °C and a good crosslinking efficiency indicated by a gel content of 90% were achieved for the fully bio-based polyester obtained under milder reaction conditions and dilution with DMI. Life cycle assessment was performed on selected UPRs, and comparison with a reference fossil-based resin in terms of the calculated category indicator results confirmed the lower environmental impact of the newly prepared bio-based polyesters.

Copolymerization of a Bisphenol a Derivative and Elemental Sulfur by the RASP Process

Fossil fuel refining produces over 70 Mt of excess sulfur annually from for which there is currently no practical use. Recently, methods to convert waste sulfur to recyclable and biodegradable polymers have been delineated. In this report, a commercial bisphenol A (BPA) derivative, 2,2′,5,5′-tetrabromo(bisphenol A) (Br4BPA), is explored as a potential organic monomer for copolymerization with elemental sulfur by RASP (radical-induced aryl halide-sulfur polymerization). Resultant copolymers, BASx (x = wt% sulfur in the monomer feed, screened for values of 80, 85, 90, and 95) were characterized by thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. Analysis of early stage reaction products and depolymerization products support proposed S–Caryl bond formation and regiochemistry, while fractionation of BASx reveals a sulfur rank of 3–6. Copolymers having less organic cross-linker (5 or 10 wt%) in the monomer feed were thermoplastics, whereas thermosets were accomplished when 15 or 20 wt% of organic cross-linker was used. The flexural strengths of the thermally processable samples (>3.4 MPa and >4.7 for BAS95 and BAS90, respectively) were quite high compared to those of familiar building materials such as portland cement (3.7 MPa). Furthermore, copolymer BAS90 proved quite resistant to degradation by oxidizing organic acid, maintaining its full flexural strength after soaking in 0.5 M H2SO4 for 24 h. BAS90 could also be remelted and recast into shapes over many cycles without any loss of mechanical strength. This study on the effect of monomer ratio on properties of materials prepared by RASP of small molecular aryl halides confirms that highly cross-linked materials with varying physical and mechanical properties can be accessed by this protocol. This work is also an important step towards potentially upcycling BPA from plastic degradation and sulfur from fossil fuel refining.

Thermostable α-Glucan Phosphorylase-Catalyzed Enzymatic Copolymerization to Produce Partially 2-Deoxygenated Amyloses

α-Glucan phosphorylase catalyzes the enzymatic polymerization of α-d-glucose 1-phosphate (Glc-1-P) monomers from a maltooligosaccharide primer to produce α(1→4)-glucan—i.e., amylose. In this study, by exploiting the weak specificity for the substrate recognition of a thermostable α-glucan phosphorylase (from Aquifex aeolicus VF5), we investigated the enzymatic copolymerization of 2-deoxy-α-d-glucose 1-phosphate (dGlc-1-P), which was produced in situ from d-glucal, with Glc-1-P to obtain non-natural heteropolysaccharides composed of α(1→4)-linked dGlc/Glc units—i.e., partially 2-deoxygenated amylose. The reactions were carried out at different monomer feed ratios using a maltotriose primer at 40 °C for 24 h. The products were precipitated from the reaction medium, isolated by centrifugation, and subjected to 1H NMR spectroscopic and powder X-ray diffraction measurements to evaluate their chemical and crystalline structures, respectively. Owing to its amorphous nature, the partially 2-deoxygenated amylose with adapted unit ratios formed a film when subjected to a casting method.