Synthesis of a Catechol-Based Poly(ether ether ketone) (“o-PEEK”) by Classical Step-Growth Polymerization and by Entropically Driven Ring-Opening Polymerization of Macrocyclic Oligomers

Optimized Polymeric Membranes for Water Treatment: Fabrication, Morphology, and Performance

Conventional polymers, endowed with specific functionalities, are extensively utilized for filtering and extracting a diverse set of chemicals, notably metals, from solutions. The main structure of a polymer is an integral part for designing an efficient separating system. However, its chemical functionality further contributes to the selectivity, fabrication process, and resulting product morphology. One example would be a membrane that can be employed to selectively remove a targeted metal ion or chemical from a solution, leaving behind the useful components of the solution. Such membranes or products are highly sought after for purifying polluted water contaminated with toxic and heavy metals. An efficient water-purifying membrane must fulfill several requirements, including a specific morphology attained by the material with a specific chemical functionality and facile fabrication for integration into a purifying module Therefore, the selection of an appropriate polymer and its functionalization become crucial and determining steps. This review highlights the attempts made in functionalizing various polymers (including natural ones) or copolymers with chemical groups decisive for membranes to act as water purifiers. Among these recently developed membrane systems, some of the materials incorporating other macromolecules, e.g., MOFs, COFs, and graphene, have displayed their competence for water treatment. Furthermore, it also summarizes the self-assembly and resulting morphology of the membrane materials as critical for driving the purification mechanism. This comprehensive overview aims to provide readers with a concise and conclusive understanding of these materials for water purification, as well as elucidating further perspectives and challenges.

Combined Molecular Dynamics and DFT Simulation Study of the Molecular and Polymer Properties of a Catechol-Based Cyclic Oligomer of Polyether Ether Ketone

The geometrical, energetic, noncovalent, and material properties of a catechol-based cyclic oligomer of Polyether Ether Ketone (PEEK) called o-PEEK were investigated using Molecular Dynamics (MD) and Density Functional Theory (DFT) simulations. The DFT (and MD) calculation performed with the PBEsol functional (and COMPASS II force field) gave a density of 1.39 (and 1.36) gcm⁻³ and a volume of 2744.5 (and 2808.5) cm³ for o-PEEK and are comparable with the corresponding experimental values of 1.328 gcm⁻³ and 2884.6 cm³, respectively. The absolute values of the glass transition temperature (T_g) MD simulated using the unit-cell and 2 × 2 × 2 supercell geometries of the o-PEEK system were 424.4 and 428.6 K, respectively. Although these values slightly differ from each other, both are close to the experiment (T_g = 418.2 K). The results of the (charge) density gradient analysis suggest that the supramolecular assembly between the o-PEEK oligomers in the experimentally observed infinite semi-crystal is driven by a wide range of noncovalent interactions. While the individual local interactions between the oligomers were recognized to be weak-to-medium in strength and are theoretically difficult to quantify, the B97-D3/cc-pVTZ level stabilization energy responsible for the formation of each of the five binary complex configurations extracted from the PBEsol relaxed 2 × 2 × 2 supercell geometry of the o-PEEK system was calculated to vary between –3.5 and –33.0 kcal mol⁻¹.

Synthesis and properties of novel copolymers of poly(ether ketone ketone) and poly(ether sulfone ether ketone ketone) containing 1,4-naphthylene moieties

A new monomer containing naphthalene and sulfone groups, 4,4′-bis(1-naphthoxy)diphenylsulfone (BNODPS), was easily prepared by the condensation reaction of 4,4′-dichlorodiphenylsulfone with 1-naphthol in the presence of base in dimethyl sulfoxide. Novel copolymers of poly(ether ketone ketone) and poly(ether sulfone ether ketone ketone) containing 1,4-naphthylene moieties were synthesized by the electrophilic Friedel–Crafts acylation copolycondensation of terephthaloyl chloride with a mixture of diphenyl ether (DPE) and BNODPS, over a wide range of DPE/BNODPS molar ratios, in the presence of anhydrous AlCl3 and N-methylpyrrolidone (NMP) in 1,2-dichloroethane. The polymers obtained were characterized by different physicochemical techniques. The copolymers with 5–25 mol% BNODPS are semicrystalline and had remarkably increased Tgs and decreased Tms over the wholly para-linked poly(ether ketone ketone) due to the incorporation of bulky and rigid 1,4-naphthylene moieties and flexible sulfone linkages in the main chains. The copolymer VI with 25 mol% BNODPS had not only high Tg of 185°C but also moderate Tm of 335°C, having good potential for melt processing. The copolymer VI had tensile strength of 102.2 MPa, Young’s modulus of 2.78 GPa, and elongation at break of 15.9% and exhibited high thermal stability and good resistance to organic solvents.

Synthesis and properties of novel poly(aryl ether ketone)s containing both 2,6-naphthylene and 1,4-naphthylene units

A new monomer containing naphthalene, namely 4,4′-di(1-naphthoxy)benzophenone (DNOBN), was prepared by the condensation reaction of 4,4′-difluorobenzophenone with 1-naphthol in the presence of base in N-methylpyrrolidone (NMP). Novel poly(aryl ether ketone)s containing both 2,6-naphthylene and 1,4-naphthylene units were synthesized by the electrophilic Friedel-Crafts acylation polycondensation of terephthaloyl chloride with a mixture of 2,6-bis(4-phenoxybenzoyl)naphthalene (BPOBN) and DNOBN, over a wide range of BPOBN/DNOBN molar ratios, in the presence of anhydrous AlCl3 and NMP in 1,2-dichloroethane (DCE). The copolymers obtained were characterized by different physicochemical techniques. The copolymers with 10–20 mol% DNOBN are semicrystalline and had remarkably increased Tgs over commercially available poly(ether ether ketone) and poly(ether ketone ketone) due to the incorporation of 2,6-naphthylene and 1,4-naphthylene moieties in the main chains. The copolymer IV with 20 mol% DNOBN had not only high Tg of 189°C, but also moderate Tm of 338°C, having good potential for melt processing. The copolymer IV had tensile strength of 102.2 MPa, Young’s modulus of 3.25 GPa, and elongation at break of 18.5% and exhibited high thermal stability and excellent resistance to organic solvents.

Synthesis and properties of novel random copolymers of poly(ether ketone ether ketone ketone)–poly(ether ketone sulfone imide)

The monomer containing sulfone and imide linkages, namely bis[4-( p-phenoxybenzoyl)-1,2-benzenedioyl]- N, N, N′, N′-4,4′-diaminodiphenyl sulfone (BPBDADPS), was prepared by the Friedel–Crafts reaction of bis(4-chloroformyl-1,2-benzenedioyl)- N, N, N′, N′-4,4′-diaminodiphenyl sulfone with diphenyl ether. Novel random copolymers of poly(ether ketone ether ketone ketone)–poly(ether ketone sulfone imide) were synthesized by the electrophilic Friedel–Crafts acylation polycondensation of terephthaloyl chloride with a mixture of 4,4′-diphenoxybenzophenone and BPBDADPS in the presence of anhydrous aluminum chloride and N-methylpyrrolidone in 1,2-dichloroethane. The random copolymers with 10–35 mol% BPBDADPS are semicrystalline and had remarkably increased glass transition temperatures ( Tgs) over the conventional poly(ether ether ketone) and poly(ether ketone ketone) due to the incorporation of polar sulfone and imide linkages in the main chains. The copolymers IV and V with 30–35 mol% BPBDADPS had not only high Tgs of 184–186°C but also moderate melting temperatures ( Tms) of 336–340°C, having good potential for melt processing. The copolymers IV and V had tensile strengths of 100.8–103.6 MPa, Young’s moduli of 2.31–2.48 GPa, and elongations at break of 10.9–12.4% and exhibited high thermal stability and good resistance to organic solvents.

Synthesis and properties of novel copolymers of poly(ether ketone ketone) and poly(ether ether ketone ketone) containing amide and sulfone linkages

N, N′-Bis(4-phenoxybenzoyl)-4,4′-diaminodiphenyl sulfone (BPBDAS) was prepared by the condensation of 4,4′-diaminodiphenyl sulfone with 4-phenoxybenzoyl chloride in N, N-dimethylacetamide. Novel copolymers of poly(ether ketone ketone) (PEKK) and poly(ether ether ketone ketone) containing amide and sulfone linkages (PEASAEKK) were synthesized by electrophilic Friedel–Crafts copolycondensation of terephthaloyl chloride with a mixture of diphenyl ether (DPE) and BPBDAS over a wide range of DPE/BPBDAS molar ratios, in the presence of anhydrous AlCl3 and N-methylpyrrolidone in 1,2-dichloroethane. The influences of the reaction conditions on the preparation of copolymers were examined. The copolymers obtained were characterized by different physicochemical techniques. The copolymers containing 10–25 mol% BPBDAS are semicrystalline and had remarkably increased Tgs compared to the commercially available poly(ether ether ketone) and PEKK due to the incorporation of amide and sulfone linkages in the main chains. The copolymer V with 25 mol% BPBDAS had not only high Tg of 187°C but also moderate Tm of 343°C, with good potential for melt processing. The copolymer V had a tensile strength of 102.7 MPa, Young’s modulus of 2.19 GPa, and elongation at break of 14.1%, and it also exhibited high thermal stability and good resistance to organic solvents.

Synthesis and characterization of novel poly(aryl ether ketone)s containing sulfone and imide linkages in the main chains

A new monomer, bis[4-(p-phenoxybenzoyl)-1,2-benzenedioyl]-N,N,N′,N′-4,4′-diaminodiphenyl sulfone (BPBDADPS), was prepared by the Friedel–Crafts reaction of bis(4-chloroformyl-1,2-benzenedioyl)-N,N,N′,N′-4,4′-diaminodiphenyl sulfone (BCBDADPS) with diphenyl ether (DPE). Novel poly(aryl ether ketone)s containing sulfone and imide linkages in the main chains (PAEKSI) were synthesized by electrophilic solution polycondensation of terephthaloyl chloride (TPC) with a mixture of DPE and BPBDADPS under mild conditions. The copolymers obtained were characterized by different physico-chemical techniques. The copolymers with 10–30 mol% BPBDADPS are semi-crystalline and had remarkably increased Tg values over commercially available PEEK and PEKK due to the incorporation of sulfone and imide linkages in the main chains. The copolymers III and IV with 20–30 mol% BPBDADPS had not only high Tg values of 180–187 °C, but also moderate Tm values of 338–341 °C, having good potential for the melt processing. The copolymers III and IV had tensile strengths of 100.7–104.2 MPa, Young’s moduli of 2.31–2.44 GPa, and elongations at break of 12.2–14.7% and exhibited high thermal stability and good resistance to organic solvents.

Novel soluble aromatic poly(ether amide sulfone amide ether ketone ketone)s by electrophilic solution polycondensation

A new monomer, N,N '-bis(4-phenoxybenzoyl)-4,4'-diaminodiphenyl sulfone (BPBDAS), was prepared by the condensation of 4,4'-diaminodiphenyl sulfone with 4-phenoxybenzoyl chloride in N,N-dimethylacetamide. Novel soluble aromatic poly(ether amide sulfone amide ether ketone ketone)s (PEASAEKKs) were synthesized by electrophilic solution copolycondensation of BPBDAS with a mixture of terephthaloyl chloride and isophthaloyl chloride in the presence of anhydrous aluminum chloride and N-methylpyrrolidone in 1,2-dichloroethane. The influences of reaction conditions on the preparation of polymers were examined. All these polymers are amorphous and soluble in aprotic polar solvents due to the incorporation of 4,4'-dibenzoylaminodiphenyl sulfone moieties in the main chain. Thermal analyses showed that the polymers had high Tg values of 236—259 °C and exhibited high thermal stability. All the polymers formed transparent, strong, and flexible films, with tensile strengths of 97.6—103.7 MPa, Young’s moduli of 2.12—2.45 GPa, and elongations at break of 10.6—13.8%.