Porous membranes
of recycled poly(ethylene terephthalate) (PET)
were prepared by nonsolvent-induced phase separation (NIPS) and evaluated
for the first time for the filtration in high temperature solvents
and other harsh environments. The PET was recycled from commercial
water bottles. The morphology, pore size, and pore density were optimized
by varying the composition of the polymer concentration in the casting
solution, the solvent, and the nonsolvent bath in conditions of controlled
humidity and temperature. Poly(ethylene glycol) (PEG) of 0.2 and 1
kg mol–1 was used as an additive and pore inducing
agent. The filtration performance of the membranes was tested under
different solvents and temperatures. The obtained PET membranes were
successfully applied for ultrafiltration with a MWCO of 40 kg mol–1 in dimethylformamide (DMF) at temperatures up to
100 °C. PET membranes were found to be resistant to a wide variety
of solvents as well as in chlorine and acid medium. They could be
used as porous support for thin-film composite membranes and for different
applications requiring high chemical and heat resistance.
Reversible stepwise chain growth in linear Cu assemblies can be achieved by using the dynamic, unsymmetric naphthyridinone-based ligand scaffolds L1 and L2. With the same ligand scaffolds, the length of the linear copper chain can be varied from two to three and four copper atoms, and the nuclearity of the complex is easily controlled by the stepwise addition of a Cu precursor to gradually increase the chain length, or by the reductive removal of Cu atoms to decrease the chain length. This represents a rare example of a stepwise controlled chain growth in extended metal atom chains (EMACs). All complexes are formed with excellent selectivity, and the mutual transformations of the complexes of different nuclearity were found to be fast and reversible. These unusual rearrangements of metal chains of different nuclearities were achieved by a stepwise "sliding" movement of the naphthyridinone bridging fragment along the metal chain.
The selective formation of heterobimetallic PtII/CuI complexes demonstrates how facile bond activation processes can be achieved by altering the reactivity of common organoplatinum compounds through their interaction with another metal center.
Efficient
and ambient synthesis of aromatic polyimides (PIs) from
readily available starting materials remains a very challenging task
in polymer chemistry. Herein, we report for the first time a robust,
one-step synthesis of organo-soluble functional aromatic PIs. Room
temperature, metal-free, superacid (TFSA)-catalyzed step polymerization
of aryl-terminated diimides with carbonyl compounds (2,2,2-trifluoroacetophenone
and indoline-2,3-dione (isatin)) afforded 14 high-molecular-weight,
linear, film-forming PIs. The effect of structural variation of the
dianhydride segment, the amount of catalyst, and monomer concentration
were studied. The PIs were obtained in quantitative yields, with high
thermal stabilities up to 525 °C and 55% weight residue at 800
°C under an inert atmosphere and number-average molecular weights
(M
n) in a range of 51–195 kg mol–1. Well-controlled proportions of the functional phenolic
hydroxyl groups (at the ortho-position to the imide ring) and diaryloxindole
reactive sites were introduced into macromolecules during polyimide
syntheses, while pendent allyl and propargyl groups were formed by
the chemical postpolymerization reactions. Subsequent modifications
of the reactive sites using click-chemistry can afford multifunctional
polymers with tunable properties. The thermal postpolymerization modification
of polyhydroxyimides converts them into polybenzoxazoles (so-called
thermally rearranged polymers).
Poly(ether ether ketone) (PEEK) is one of the most attractive polymers for organic solvent resistance applications because of its high thermal and organic solvent resistance. However, one of the main disadvantages is that PEEK has to be processed by using harsh solvents, such as methanesulfonic and sulfuric acid. Here, we report for the first time the preparation of PEEK membranes for organic solvent filtration by using common organic solvents. The preparation method consists of the conversion of PEEK into a soluble precursor, followed by dissolution in a mixture of tetrahydrofuran and N,N-dimethylacetamide. The resulting solution is used to obtain the membranes by phase inversion. In the second step, we convert the PEEK precursor to PEEK by treating the obtained membranes with an aqueous acid solution. The resulting PEEK membranes have good permeance and rejection, along with high stability in organic solvents and at high temperatures (up to 140 °C). This procedure opens many possibilities for processing PEEK into membranes by using common techniques to obtain flat sheet membranes or hollow fibers for a broad range of applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.