Low-temperature processing of ‘baroplastics’ by pressure-induced flow

Abstract

The manufacturing of plastics traditionally involves melt processing at temperatures typically greater than 200 degrees C-to enable extrusion or moulding under pressure into desired forms-followed by solidification. This process consumes energy and can cause substantial degradation of polymers and additives (such as flame retardants and ultraviolet stabilizers), limiting plastics performance and recyclability. It was recently reported that the application of pressure could induce melt-like behaviour in the block copolymer polystyrene-block-poly(n-butyl methacrylate) (PS-b-PBMA), and this behaviour has now been demonstrated in a range of other block copolymer systems. These polymers have been termed baroplastics. However, in each case, the order-to-disorder transition, which gives rise to the accompanying change in rheology from soft solid to melt, was observed at temperatures far exceeding the glass transition temperatures (T(g)) of both components. Here we show that baroplastic systems containing nanophase domains of one high-T(g) and one low-T(g) component can exhibit melt-like flow under pressure at ambient temperature through an apparent semi-solid partial mixing mechanism that substantially preserves the high-T(g) phase. These systems were shredded and remoulded ten times with no evident property degradation. Baroplastics with low-temperature formability promise lower energy consumption in manufacture and processing, reduced use of additives, faster production and improved recyclability, and also provide potential alternatives to current thermoplastic elastomers, rubber-modified plastics, and semi-crystalline polymers.

Polymers with Multiple Hydrogen-Bonded End Groups and Their Blends

“…Molecular weight distributions were monomodal, and polydispersities were typically in the range of 1.10-1.15. Absolute molecular weights were measured by 1 Figures 1 and 2). Any residual water present in the polymers is expected to affect the melt phase behavior, so all polymers were thoroughly dried after isolation by heating to 50°C in a vacuum oven over P 2 O 5 overnight.…”

“…The resulting solid was purified by recrystallization from ethanol, giving the product as a white solid in 55% yield (4.50 g). 1 …”

“…The resulting solid was purified by recrystallization from ethanol, giving the product as a white solid in 63% yield (5.36 g). 1 H NMR (CDCl 3 ): δ ) 12.91 (br, 1H), 11.91 (br, 1H), 10.45 (br, 1H), 5.74 (s, 1H), 4.27 (t, 2H, J ) 6 Hz), 3.54 (t, 2H, J ) 6 Hz), 2.19 (s, 3H), 1.89 (s, 6H), 1.52 (s, 3H) ppm. 13 …”

“…The organic layer was dried over MgSO 4 , concentrated, and purified by column chromatography using chloroform as the eluent to give the product as a white solid in 89% yield (0.94 g). 1 (2S)-1-(7-(2-Ethylhexanamido)-1,8-naphthyridin-2-ylamino)-1-oxopropan-2-yl 2-Bromopropanoate, 5. A solution of 2-ethyl-N-(7-((S)-2-hydroxypropanamido)-1,8-naphthyridin-2-yl)hexanamide, 4 (1.00 g, 2.79 mmol), and triethylamine (0.295 g, 2.92 mmol) in tetrahydrofuran (5 mL) was cooled to 0°C, after which 2-bromopropionyl bromide (1.37 g, 6.35 mmol) was added dropwise via a syringe.…”

“…Baroplastics, for example, are block copolymers that display meltlike flow at temperatures below the glass transition of the higher T g component (depending on the composition) through pressureinduced partial mixing of weakly interacting blocks. 1,2 Alternately, supramolecular polymers consisting of multiple hydrogenbonding telechelic oligomers were shown to have highly temperature dependent properties, 3,4 allowing them to be processed at relatively low temperatures due to the reversible breaking of noncovalent backbone linkages, while at room temperature these linkages are strongly bound, producing an elastic solid.…”