Synthetic cationic polyelectrolytes (CPEs) serve as coagulation and flocculation agents in wastewater treatment due to a synergy of inherent electrostatic interactions and hydrophilic properties. In wastewater treatment, CPEs act as coagulation and flocculation agents to aggregate impurities and enable water purification. New health and environmental-related regulations provide motivation for government agencies and industrial companies to reuse wastewater. Chemical structure, molecular weight, charge density and functionality of CPEs provide tailorability for specific purification needs. Cationic polyacrylamides, ammonium-based polymers, poly(allyldimethyl-ammonium chloride) and epichlorohydrin/dimethylamine-based polymers are the most common CPEs used as coagulation and flocculation agents because they are economical and water soluble with tunable charge densities at high molecular weights. Free radical polymerization, step-growth polymerization and post-polymerization modification methods afford each polymer system. This review highlights recent advancements in synthetic methods to yield CPEs, structure−property relationships as related to flocculation efficiency and a summary of their toxicity and environmental impact.

Fabrication of personalized dosage oral pharmaceuticals using additive manufacturing (AM) provides patients with customizable, locally manufactured, and cost-efficient tablets, while reducing the probability of side effects. Binder jetting AM has potential for fabrication of customized dosage tablets, but the resulting products lack in strength due to solely relying on the binder to produce structural integrity. The selection of polymeric binders is also limited due to viscosity restraints, which limits molecular weight and concentration. To investigate and ameliorate these limitations, this article reports a comprehensive study of linear and 4-arm star poly­(vinyl pyrrolidone) (PVP) over a range of molecular weights as polymeric binders for binder jetting AM and their effect on physical tablet properties. Formulation of varying molecular weights and concentrations of linear and 4-arm star PVP in deionized water and subsequent jetting revealed relationships between the critical overlap concentrations (C*) and jettability on binder jetting systems with thermal inkjet printheads. After printing with a commercially available ZCorp Spectrum Z510 printer with an HP11 printhead with a lactose and powdered sugar powder bed, subsequent measurement of compressive strength, compressive modulus, and porosity revealed structure–property relationships between molecular weight, polymer concentration, and linear and 4-arm star architectures with physical properties of binder jetted tablets. This study elucidated that the dominating factor to increase compressive strength of a tablet is dependent on the weight percent of the polymer in the binder, which filled interstitial voids between powder particles. Because 4-arm star polymers have lower solution viscosities compared to linear analogues at the same molecular weights, they were jettable at higher concentrations, thus producing the strongest tablets at a compressive strength of 1.2 MPa. Finally, the inclusion of an active pharmaceutical ingredient (API), acetaminophen, revealed maintenance of the tablet physical properties across 5–50 total wt % API in each tablet.

Vat photopolymerization of a trimethylammonium ethyl acrylate chloride solution (TMAEA) resulted in a well-defined, fully soluble, 3D printed rook.

New polymers with a phosphazene backbone and both 2,2,2-trifluoroethoxy- and phenoxy-functionalized cyclotriphosphazene substituents exist in three phases depending on the side group ratios. At low concentrations of the bulky substituents (up to ∼7 mol %), the polymers are semicrystalline thermoplastics, with properties that are minor variations of poly­[bis­(2,2,2-trifluoroethoxy)­phosphazene]. However, after the incorporation of between ∼7 mol % and ∼20 mol % of the bulky cyclic trimeric side groups, the polymers lose their semicrystalline properties and become amorphous elastomers. At still higher trimer loadings (>20 mol %) the materials develop gum-like behavior. The elastomeric phase appears to be generated by interdigitation or agglomeration of the bulky aryloxy-cyclotriphosphazene side groups, which act as quasi-physical cross-links between the polymer chains. The presence of these interactions allows the materials to experience high strain values before rupture (up to 1000%), and elastic recovery of more than 85% of the original dimensions when stressed up to 60% of the break elongation over four cycles. In addition, the chemical and physical nature of the substituents on the cyclic trimeric side groups alters the physical characteristics of the polymer in a way that provides a facile method to tune the properties.

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