Getting past the hype about 3-D printing

The hope for additive manufacturing is that it will revolutionize manufacturing.1 Although additive manufacturing — also known as 3-D printing — was developed back in the 1980s, it has garnered increased attention in recent years as managers look for ways to improve efficiency and reduce production costs. Managers hope that much the way GE’s new printed nozzle for jet engines has reduced the need for expensive materials and energy,2 3-D-printed parts will cut lead times and make supply chains more efficient in a wide range of settings.3\u3cbr/\u3e\u3cbr/\u3eDespite the potential of additive manufacturing, we believe that near-term expectations for it are overblown. We base this conclusion on our research, which included 80 interviews as well as extensive study of the literature on the history of materials and process technologies, industry meetings, and factory visits.4 (See “About the Research.”

Synergistic Effect of 1‑Butyl-3-methylimidazolium Hexafluorophosphate and DMSO in the SARA ATRP at Room Temperature Affording Very Fast Reactions and Polymers with Very Low Dispersity

An unusual synergistic effect between 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF₆) and dimethyl sulfoxide (DMSO) mixtures is reported for the supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) of methyl acrylate (MA) using a catalytic system composed by sodium dithionate (Na₂S₂O₄) and CuBr₂/Me₆TREN (Me₆TREN: tris­[2-(dimethylamino)­ethyl]­amine) at room temperature. To the best of our knowledge, the use of ionic liquids (IL) has never been reported for the SARA ATRP. The kinetic data obtained for a broad range of target molecular weights revealed very fast polymerization rates, low dispersity values (<i>Đ</i> < 1.05) and well-defined chain-end functionalities

Sulfolane: an Efficient and Universal Solvent for Copper-Mediated Atom Transfer Radical (co)Polymerization of Acrylates, Methacrylates, Styrene, and Vinyl Chloride

A very fast and controlled atom transfer radical (co)­polymerization (ATRP) of acrylates, methacrylates, styrene, and vinyl chloride is reported in a single dipolar aprotic solvent, sulfolane, with the use of ppm amount of the copper catalyst. The observed rates of polymerization (<i>k</i>_p^app) of the monomers studied are similar to those reported using dimethyl sulfoxide (DMSO) and other polar solvents typically employed in single electron transfer (SET)-mediated atom transfer radical polymerization (ATRP) processes. As proof-of-concept, ABA type block copolymers of polystyrene-<i>b</i>-poly­(vinyl chloride)-<i>b</i>-polystyrene and poly­(methyl acrylate)-<i>b</i>-poly­(vinyl chloride)-<i>b</i>-poly­(methyl acrylate) were prepared for the first time using a reversible deactivation radical polymerization (RDRP) method in a single solvent. The quantitative preservation of halide chain-ends was confirmed by ¹H NMR and MALDI-TOF analysis as well as by the complete shift of the GPC traces. The results presented establish an innovative and robust system to afford a vast portfolio of (co)­polymers in a single widely used industrial solvent

Aqueous RDRP in the Presence of Cu⁰: The Exceptional Activity of Cu^I Confirms the SARA ATRP Mechanism

Polymerizations and mechanistic studies have been performed to understand the kinetic pathways for the polymerization of the monomer oligo­(ethylene oxide) monomethyl ether acrylate (OEOA) in aqueous media. Typically, the medium consisted of 18 wt % OEOA in water, in the presence of Cu catalysts coordinated by tris­[2-(dimethylamino)­ethyl]­amine (Me₆TREN). Well-controlled polymerization of OEOA can be achieved in the presence of halide anions and Cu wire with ≲600 ppm of soluble Cu^II species, rather than previously reported ca. 10 000 ppm of Cu^II and Cu⁰ particles formed by predisproportionation of Cu^I prior to monomer and initiator addition. The mechanistic studies conclude that even though disproportionation is thermodynamically favored in aqueous media, the SARA ATRP, not SET-LRP, mechanism holds in these reactions. This is because alkyl halides are much more rapidly activated by Cu^I than by Cu⁰ (contribution of Cu⁰ to activation is <1%). Because of the high activity of Cu^I species toward alkyl halide activation, [Cu^I/Me₆TREN] in solution is very low (<5 μM) and classical ATRP equilibrium between Cu^I and Cu^II species is maintained. Although in aqueous media disproportionation of Cu^I/Me₆TREN is thermodynamically favored over comproportionation, unexpectedly, in the presence of alkyl halides, i.e., during polymerization, disproportionation is kinetically minimized. Disproportionation is slow because its rate is proportional to [Cu^I/Me₆TREN]² and [Cu^I/Me₆TREN] is very small. Thus, during polymerization, comproportionation is 10⁴ times faster than disproportionation, and the final thermodynamic equilibrium between disproportionation and comproportionation could be reached only after polymerization is completed. Activation of alkyl halides by Cu^I/Me₆TREN in aqueous media occurs 8 orders of magnitude faster than disproportionation