Polycondensation Research Articles

Leveraging Electron Push-Pull Effect for Catalytic Polymerization and Degradation of a Cyclobutane Monomer System.

Ring-opening polymerization (ROP) offers a striking solution to solve problems encountered in step-growth condensation polymerization, including precise control over molecular weight, molecular weight distribution, and topology. This has inspired our interest in ROP of cycloalkanes with an ultimate goal to rethink polyolefins, which clearly poses a number of challenges. Practicality of ROP of cycloalkanes is actually limited by their low polymerizability and elusive mechanisms which arise from significantly varied ring size and non-polar C-C bonds in monomers. In this work, by using Lewis acid/Brønsted base/C(sp3)-H initiator system previously developed in our laboratory, we focus on cyclobutanes and explore the positional and electronic effects of substituents on the ring, namely electron push-pull effect, in promoting controlled polymerization to afford densely functionalized poly(cyclobutanes), as well as catalytic degradation of obtained polymers for upcycling. More importantly, experiments and DFT calculations unveil considerable population of Lewis-acid-induced thermostabilized 1,4-zwitterions, which distinguish cyclobutanes from cyclopropanes and others. All these findings would shed light on catalytic synthesis and degradation of saturated all-carbon main-chain polymers, as well as small molecule transformations of cyclobutanes.

Fabrication of hybrid polyimide composites containing Ladder-like poly(phenyl-co-glycidoxypropyl)silsesquioxane)

Ladder-like structured poly(phenyl-co-glycidoxypropyl) silsesquioxanes with different ratios of phenyl to glycidyl group (LPS64 and LPS 82) were synthesized using simple hydrolysis reaction followed by condensation polymerization of phenyltrimethoxysilane (PTMS) and (3-glycidyloxypropyl)trimethoxysilane (GPTMS). Two series of hybrid polyimide composites (PI/LPS64 and PI/LPS82) with different contents of LPS (10, 20, and 30 wt%) were prepared by the chemical reaction of epoxy groups in LPS64 or LPS82 and the terminal amine groups in poly(amic acid). The dielectric constant (k) of hybrid PI composites (k = 1.3) was lower than that of pure polyimide (k = 2.9) and the degree of roughness was increased according to the increase of LPS contents. The dispersion of LPS in the PI matrix was improved due to the chemical bonding between LPS and PI. The thermal stability of PI/LPS82 was higher than that of PI/LPS64 due to the enhanced π-π stacking between PI matrix and LPS82 with more phenyl groups as compared to LPS64.

Novel nano magnesium oxide modified hybrid emulsion for antimicrobial coating

Purpose The purpose of this paper is to develop an inorganic-organic hybrid emulsion polymer using grafted hyperbranched alkyd modified with nanometal oxide and to study the performance of the developed hybrid emulsion in paint formulation with respect to antimicrobial and other properties. Design/methodology/approach A novel hybrid emulsion polymer was synthesized by grafting of vinyl acetate (VAM), vinyl ester of versatic acid (VeoVa 10) monomers onto hyperbranched alkyd resin and incorporation of nano magnesium oxide (MgO) into the hybrid resin matrix during dispersion of resin in water. Subsequently, paint was prepared by using this hybrid emulsion followed by a performance study. Findings The performance of nano MgO modified into VAM and VeoVa 10 grafted hyperbranched alkyd resulted in unique properties of coating especially antimicrobial activity. Research limitations/implications In the present study, soya fatty acid, polyol and di basic acid have been used to prepare hyperbranched alkyd by condensation polymerization. Monomers like VAM and VeoVa 10 used for grafting onto hyperbranched alkyd and nano MgO have been incorporated into hybrid resin matrix during emulsification of hybrid resin in water. Practical implications Grafting of VAM and VeoVa 10 onto hyperbranched alkyd along with in situ incorporation of nano MgO in resin matrix is an effective technique to achieve excellent coating properties. Originality/value Nano MgO modified VAM and VeoVa 10 grafted hyperbranched alkyd-based hybrid emulsion can be used as binder in water-based metal primer, direct to metal (DTM) coating as well as topcoat application. The developed system has antimicrobial properties as well as superior mechanical properties.

A wide range of modified alkyd resins based on a new source of dicarboxylic acid as a binder for anticorrosive paint

Purpose This paper aims to prepare alkyd protective paint by using modified alkyd with 3,6-dichloro benzo[b]thiophene-2-carbonyl glutamic acid (DCBTGA) as a source of dicarboxylic acid and evaluating their anticorrosive properties compared with those of unmodified alkyd coatings for steel protection. Design/methodology/approach Short, medium and long oil alkyds, which represented as (0, 10, 20 and 30% excess-OH) according to the resin constants (Patton, 1962), were prepared through a condensation polymerization reaction via a solvent process in a one-step reaction. The modification of alkyd was carried out by using DCBTGA as a source of dicarboxylic acid. The prepared modified alkyd was confirmed by IR and NMR spectral analysis. The physicochemical, mechanical and anticorrosion performance properties of the considered modified coating formulations against unmodified blank coating were studied to confirm their application efficiency. Findings The best results in terms of physicochemical, mechanical and anticorrosion performance properties were found according to the following of this order activity: 30 replacements of the modifier (DCBTGA) for each hydroxyl continent were 30% Ex-OH > 20% Ex-OH > 10% Ex-OH > 0% Ex-OH, compared with that formulation containing unmodified alkyd, especially with increasing the modifier percent. Originality/value The prepared DCBTGA-modified resins can be used for different applications based on the type of alkyd and application.

Donor-acceptor covalent organic framework/ZnIn2S4 core-shell structure S-scheme heterostructure for efficient photocatalytic hydrogen evolution

Covalent organic frameworks (COFs) show promising prospect as the photocatalysts with advantages of exceptional light adsorption capability, large specific surface area, and adjustable band structure. However, COFs usually suffer from severe recombination of photogenerated carriers. Therefore, there is an urgent demand to design effective COF-based heterostructures to enhance the separation of carriers. In this work, a porphyrin-based COF with electron donor-acceptor structure is synthesized via condensation polymerization by using 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAPPP) and N,N,N',N'-tetra(4-formylphenyl)benzidin (NFPBD) as the donor and acceptor, respectively. Subsequently, ZnIn2S4 (ZIS) are successfully in-situ grown on the surface of porphyrin-based COF, forming a novel core-shell structure. The in-situ synthesized ZIS with positive charges can be easily adsorbed on the negatively charged sites of the COF’s surface via the electrostatic interaction. This organic/inorganic hybrid COF-ZIS heterostructure exhibits a superior photocatalytic hydrogen evolution (PHE) rate of 695 μmol g−1 h−1, approximately three times higher than that of ZIS. The construction of COF-ZIS heterostructure plays an important role in enhancing the separation and transport of photogenerated carriers, which provides more electrons at the surface of ZIS to take part in proton reduction. Electron paramagnetic resonance spectra confirm the charge carriers transfer mode in the COF-ZIS heterostructure via an S-scheme mechanism. Moreover, upon loading Pt as the cocatalyst, the heterostructure achieves an effective PHE rate of 2711 μmol g−1 h−1 along with an exceptional stability. Additionally, the COF-ZIS heterostructure reaches up to 2.45% of apparent quantum efficiency at 400 nm. Notably, the average lifetime of the COF-ZIS heterostructure increases by 43.2% and 98.9% compared to that of ZIS and the COF individually, as observed through single-particle fluorescence spectroscopy. This work gives valuable inspiration into the building of donor-acceptor COF-based S-scheme heterostructures to achieve highly effective green energy conversion by aligning band structures.

Impact of annealing temperature on the structural, morphological and optical properties of Ni doped ZnO nanostructured thin films synthesized by sol–gel methodology

Abstract Nickel doped zinc oxide (NZO) nanostructured thin films were prepared by hydrolysis and poly condensation reaction based on the sol–gel methodology. Nanostructured thin films were prepared over the glass substrate by dip coating. Prepared samples were annealed at 350 °C and 450 °C respectively to tune the desired characteristics. The XRD studies endorses the prepared films were polycrystalline in nature and high intensity sharp peaks were exhibited in (101) direction. EDAX results confirms the presence of Ni, Zn and O elements. FESEM results exhibits the spherical like morphology throughout the sample. The typical grain size of prepared samples are vary from 35 nm to 105 nm. Results of the FTIR divulges the different composition of prepared NZO samples. UV–vis spectrophotometer results reveals that the fabricated 1 at.% NZO thin films annealed at 450 °C were guaranteed to have the lowest absorbance of less than 10 %, while the 0.5 at.% NZO thin films have an energy band gap of roughly 3.08 eV. The obtained results of the prepared films are useful for devices like solar cells, optoelectronic devices, flat panel displays, anticorrosion and surface protection applicant against stainless steel etc.

Superior mechanical performance polyurethane-silicone coatings for synergistic antimicrobial and antifouling coatings

With the increasing awareness of marine ecological environment, biocide-free marine antifouling coatings have been gaining increased attention in the field of marine antifouling. Among all the antifouling approaches, constructing fouling-release coatings (FRCs) may be the most effective and economical way caused by the biocide-free. However, the low mechanical strength, weak adhesion to substrates, and poor static fouling resistance of traditional silicone-based FRCs, which limiting their applications. In this work, we synthesized a polyurethane with hydroxyl terminated polydimethylsiloxane (PDMS), polytetrahydrofuran (PTMG) and isophorone diisocyanate (IPDI) as main chains, 2,2'-Bis (hydroxymethyl)butyric acid (DMBA) as chain extender, and γ-aminopropyl triethoxysilane (KH-550) as crosslinker by condensation polymerization. Meanwhile, Triclosan (TCS) was used as an antibacterial agent and mixed into the polymer system with uniformly dispersed. We introduced urethane groups into silicone, which improved the mechanical strength (ultimate tensile strength: 1.379 MPa, elongation at break: 282%). As a result, the laboratory bioassays using bacteria (E. coli, and S. aureus) showed that the anti-bacterial efficiency could respectively reach ∼95% and ∼93%, which demonstrated an outstanding antifouling property of the D:K = 0.7:1.3/1.0. This work overcomes the low strength issue of traditional fouling-release coatings and provides a simple strategy for silicone-based polyurethane antifouling coatings.

Novel protective coating based on the prepared Cu (II) and Co (II)‐containing linoleic poly(esteramide) as new anticorrosive and antimicrobial binders for industrial applications

AbstractThis article focused on the preparation of Cu, Co (II)‐containing linoleic‐based poly(ester amide) resin and studied their use as new binders for paint formulation. The metal‐containing LPEA was carried out by in situ condensation polymerization reaction between hydroxyethyl linoleic fatty amide diol (HELA), phthalic anhydride (PA), and Cu, Co acetate. The structure of the prepared resins was confirmed by FTIR and 1H NMR spectral studies. Physicochemical, thermal analysis (TGA), surface morphology (SEM), and elemental composition (EDX) were studied by standard methods. The physicomechanical, antimicrobial, and corrosion/chemical resistance performance tests were also conducted to evaluate their coating properties. These studies revealed that (i) the incorporation of Cu, Co (II) has a significant influence on structural and physicochemical aspects. The paint formulation based on Cu, Co (II) containing LPEA showed very good results according to the corrosion resistant test evalution. (iii) Antimicrobial tests of all prepared resins were performed by agar diffusion method against Staphylococcus aureus, Bacillus cereus, Escherichia coli, Klebsiella pneumonia, and pathogenic fungal strain using standard controlled medication, ciprofloxacin/fluconazole for the comparison. (iv) Cu, Co (II) containing LPEA serve as novel binders and promising candidates for use as binders for protective coating material.

Enhanced adhesive and mechanically robust silicone-based coating with excellent marine anti-fouling and anti-corrosion performances.

Poly(dimethylsiloxane) (PDMS) is widely used in marine antifouling coatings due to its low surface energy property. However, certain drawbacks of PDMS coatings such as poor surface adhesion, weak mechanical properties, and inadequate static antifouling performance have hindered its practical applications. Herein, condensation polymerization is utilized to prepare PDMS-based polythiamine ester (PTUBAF) coatings that consist of PDMS, polytetrahydrofuran (PTMG), 2, 3, 5, 6-tetrafluoro-1, 4-benzenedimethanol (TBD) as the main chains and isobornyl acrylate(IBA) as the antifouling group. The surface adhesion to the substrate is enhanced due to the hydrogen bond between the coated carbamate group and the hydroxyl group on the surface of the substrate. Mechanical properties of PTUBAF are significantly improved due to the benzene ring and six-membered ring biphase hard structure. The strong synergistic effect of bactericidal groups and low surface energy surface endows the PTUBAF coating with outstanding antifouling performance. Due to the low surface energy surface, the PTUBAF coatings are also found to possess excellent anti-corrosion. Furthermore, since the PTUBAF coatings exhibit a visible light transmittance of 91 %, they can applied as protective films for smartphones. The proposed method has the potential to boost the production and practical applications of silicone-based coatings.

In situ polymerization of water‐induced 1,3‐phenylene diisocyanate for enhanced efficiency and stability of inverted perovskite solar cells

AbstractIn the realm of photovoltaics, organometallic hybridized perovskite solar cells (PSCs) stand out as promising contenders for achieving high‐efficiency photoelectric conversion, owing to their remarkable performance attributes. Nevertheless, defects within the perovskite layer, especially at the perovskite grain boundaries and surface, have a substantial impact on both the overall photoelectric performance and long‐term operational stability of PSCs. To mitigate this challenge, we propose a method for water‐induced condensation polymerization of small molecules involving the incorporation of 1,3‐phenylene diisocyanate (1,3‐PDI) into the perovskite film using an antisolvent technique. Subsequent to this step, the introduction of water triggers the polymerization of [P(1,3‐PDI)], thereby facilitating the in situ passivation of uncoordinated lead defects inherent in the perovskite film. This passivation process demonstrates a notable enhancement in both the efficiency and stability of PSCs. This approach has led to the attainment of a noteworthy power conversion efficiency (PCE) of 24.66% in inverted PSCs. Furthermore, based on the P(1,3‐PDI) modification, these devices maintain 90.15% of their initial efficiency after 5000 h of storage under ambient conditions of 25°C and 50 ± 5% relative humidity. Additionally, even after maximum power point tracking for 1000 h, the PSCs modified with P(1,3‐PDI) sustain 82.05% of the initial PCE. Small molecules can rationally manipulate water and turn harm into benefit, providing new directions and methods for improving the efficiency and stability of PSCs.

Hollow spherical covalent organic framework supported gold nanoparticles for photocatalytic H2O2 production

Covalent organic frameworks (COFs) are porous crystalline materials with promising applications in photocatalysis, but their performance is greatly hampered by the fast recombination of photogenerated carriers. Herein, a hollow spherical COF was synthesized via the condensation polymerization of 1,3,5-tris(4-aminophenyl)benzene and 1,3,5-benzenetricarbaldehyde, and Au nanoparticles were in-situ deposited onto the COF through NaBH4 reduction to ameliorate the photocatalytic performance. The composite exhibits impressive photocatalytic H2O2-production performance with the highest H2O2-evolution rate of 6067 μmol g−1 h−1 under visible light irradiation, which is about 1.9 times that of the pristine COF. The enhanced photocatalytic activity was ascribed to improved light absorption, abundant active Au sites, and efficient transfer and separation of photogenerated carriers in space. This work provides an avenue for designing high-performance H2O2-production photocatalysts by decorating porous COFs with active noble-metal sites.

Suzuki–Miyaura Catalyst-Transfer Condensation Polymerization for the Synthesis of Polyphenylene with Ester Side Chain by Using Stable, Reactive 1,1,2,2-Tetraethylethylene Glycol Boronate (B(Epin)) Monomer

Suzuki–Miyaura Catalyst-Transfer Condensation Polymerization for the Synthesis of Polyphenylene with Ester Side Chain by Using Stable, Reactive 1,1,2,2-Tetraethylethylene Glycol Boronate (B(Epin)) Monomer

Synthesis of well‐defined aromatic poly(amide‐ether)s via chain‐growth condensation polymerization

AbstractSince their advent over 50 years ago, aromatic polyamides have remained desirable for their thermal stability, mechanical strength, and overall versatility. Chain‐growth condensation (CGC) polymerization has made possible the synthesis of well‐defined polyamides with narrow molecular weight distributions for applications ranging from block copolymers to polymer brushes. However, the solubility of aromatic polyamides has always been a major obstacle to overcome due to aromatic π‐π stacking and intramolecular hydrogen bonding. In this article, we introduce an aryl ether functionality into the polyamide backbone to increase backbone flexibility and overall solubility. Through dropwise addition of the aryl ether functionalized monomer with a lithium disilazide base and a phenyl 4‐(dimethylcarbamoyl)benzoate initiator, we report the synthesis of a series of substituted poly(amide‐ether)s through CGC polymerization with low polydispersities (<1.1) and well‐defined molecular weights. Computational methods revealed that the polymerization mechanism is unlike other similar amino ester monomers bearing naphthalene and biphenyl aromatic units in that monomer self‐deactivation is weakened by the ether linkage. The self‐condensation of the amide‐ether monomer was nevertheless suppressed through reaction optimization, challenging the traditional requirement of monomer self‐deactivation to achieve a well‐defined CGC polymerization. The side‐chain on poly(amide‐ether) backbone was also modified from an octyl group to a 4‐(octyloxy)benzyl protecting group for postpolymerization removal with trifluoroacetic acid to yield the unsubstituted aromatic poly(amide‐ether), which showed a significant improvement in solubility from traditional unsubstituted aromatic polyamides, such as poly(p‐benzamide).

Synthesis of Poly(styrene)-g-Poly(oleic acid) Graft Copolymers via Reversible Addition/Fragmentation Transfer (RAFT) Polymerization Using a Poly Oleic Acid Macro-RAFT Agent

In this study, a new polymeric oleic acid-derived macro addition/fragmentation transfer agent was utilized to produce a poly(styrene)-g-poly(oleic acid) graft copolymer. The double bond of oleic acid was initially saturated with bromine and the condensation polymerization between the carboxylic acid and the bromide resulted in polyoleic acid with pendant bromide groups. Xanthate groups were exchanged with the bromide groups to obtain the poly(oleic acid) macro RAFT agent (Pole-Xa). Poly(styrene)-g-poly(oleic acid) (PS-g-Pole) graft copolymers were synthesized via reversible addition fragmentation transfer (RAFT) polymerization of styrene and the reaction was evaluated in view of the polymerization kinetics. The effects of polymerization temperature and reaction time on graft copolymer yield, conversion and molecular weight were investigated. In the RAFT polymerization of styrene, the rate constant (k) was found to be 1.83 × 10–3 L/mol/dk and 7.27 × 10–4 L/mol/dk for the polymerization temperatures of 80 and 90 °C, respectively. The structural characteristics and thermal properties of the obtained products were characterized using FT-IR, 1H-NMR, GPC, TGA, DSC and SEM–EDX.

Effects of curing temperature and addition of functionalized graphene oxide on corrosion barrier performance of phenol furfural polymer-amino phenolic resin composite

Phenol furfural polymer (PFP) blended amino phenolic resin (APR) and functionalized graphene oxide (FGO) dispersed PFP/APR polymer composite coatings were fabricated and evaluated their barrier performance on mild steel (MS) corrosion at different curing temperatures without using any conventional hardeners. The PFP was synthesized by condensation polymerization and blended with the prepared APR to get PFP/APR polymer composite. The GO was functionalized with 4-(trifluoromethyl) benzohydrazide (TFB) and dissipated in PFP/APR composite matrix. The synthesized materials were characterized by FT-IR, Raman, XRD, XPS, EDS, SEM and TEM techniques. The thermal stability of GO and FGO was analyzed using TGA. The fabricated composite materials were coated on MS surface and their surface morphology, anti-corrosion potential and hydrophobic character were evaluated by SEM, optical images, electrochemical impedance spectroscopy (EIS), salt spray analysis (SSA) and contact angle measurements (CA). At 70 °C curing temperature, the PFP/APR coating showed maximum coating resistance (Rc) of 1.39 × 105 Ω cm2 and charge transfer resistance (Rct) of 2.63 × 105 Ω cm2 on 60th day of immersion in 3.5 wt% NaCl solution. Addition of 0.2 wt% FGO into PFP/APR matrix reduced the ideal curing temperature to 50 °C and exhibited an admirable barrier performance even after 90 days of immersion in saline medium with a reliable Rc and Rct values of 1.24 × 105 Ω cm2, 1.93 × 105 Ω cm2 respectively, and coating capacitance (Qc) in the range of 10−9 F/cm2. The cross linking of resin and blockade of defects by nanofiller make the material highly durable and superior in extensive corrosive environment.

Lithium-copolymerized polyimide cathodes for stable and fast lithium-ion storage

Organic materials as cathodes have attracted a lot of attention for lithium-ion batteries due to their structural designability and high theoretical capacity. However, most organic polymer cathode materials, such as π-conjugated polymers, have slow diffusion of lithium ions due to closely packed structures, resulting in inferior properties. Herein, we have synthesized lithium modified polyimides by condensation polymerization between 3,4,9,10-perylenetetracarboxylic acid dianhydride and 1,2-ethylenediamine in the presence of N-(2-aminoethyl)glycine lithium salt. The lithium-copolymerized polyimides exhibit lamellar structure and have increased specific surface area and therefore lead to enhanced lithium-ion diffusion coefficient and electronic conductivity. Lithium metal half cells employing lithium modified polyimide cathodes have a high discharge capacity of 138.3 mAh g−1 at a current density of 30 mA g−1 and good cycling stability with 71 % capacity retention at a current density of 1000 mA g−1 after 5000 cycles, which are much better than those employing general polyimides.

Bio-based unsaturated polyester resin from post-consumer PET.

This study explores the utilization of post-consumer poly(ethylene terephthalate) (PET) as a material in the synthesis of styrene-free unsaturated polyester (UP) resin. The process involves glycolysis of PET waste with diethylene glycol and condensation polymerization with bio-based itaconic acid. The resulting unsaturated polyester possesses reactive methylidene functions that, in contrast to commonly employed fumarates/maleates, facilitate copolymerization with non-styrene reactive diluents. To formulate the resins, methacrylates and itaconates were used for dilution, and the curing process is achieved through a redox initiation system at room temperature, followed by post-curing at elevated temperatures. The cured formulations were characterized by their glass transition temperature, determined by DMA analysis. Mechanical properties were evaluated using standardized tests in tension, flexure, and compression. Particularly promising characteristics are observed in formulations incorporating bio-based dimethyl itaconate (DMI), allowing the formulation of materials with a high ultimate flexural strength (σf,max = 161.4 MPa) and compressive yield point (σc,yield = 131.3 MPa). Furthermore, the low volatility of DMI addresses the health, safety, and ecological concerns associated with the commonly used styrene. This technology not only presents a promising avenue for sustainable UP resin for glass fiber reinforced composites but also allows upcycling PET waste.

Alternating vs. random amphiphilic polydisulfides: aggregation, enzyme activity inhibition and redox-responsive guest release.

Herein, we report the synthesis of an alternating copolymer (ACP) with a bio-reducible amphiphilic polydisulfide backbone and highlight the impact of the alternating monomer connectivity on the self-assembly, morphology, chain-exchange dynamics, drug-release kinetics, and enzyme activity inhibition. Condensation polymerization between hydrophobic 1,10-bis(pyridin-2-yldisulfaneyl)decane and hydrophilic 2,3-mercaptosuccinic acid (1.04 : 1.00 ratio) generated amphiphilic ACP P1 (Mw = 8450 g mol-1, Đ = 1.3), which exhibited self-assembly in water, leading to the formation of an ultra-thin (height <5.0 nm) entangled fibrillar network. In contrast, structurally similar amphiphilic random copolymer P2 exhibited a truncated irregular disc-like morphology under the same conditions. It is postulated that due to the perfect alternating sequence of the hydrophobic and hydrophilic segments in P1, its immiscibility-driven aggregation in water leads to a pleated structure, which further assembles and forms the observed long fibrillar structures, similar to crystallization-driven self-assembly. In fact, wide-angle X-ray diffraction (WXRD) analysis of a lyophilized P1 sample showed sharp peaks, indicating its crystalline nature (approximately 37% crystallinity), and these were completely missing for P2. The effect of such distinct self-assembly on the chain-exchange dynamics was probed by fluorescence resonance energy transfer (FRET) using 3,3'-dioctadecyloxacarbocyanine perchlorate (DiO) and 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) as the FRET-donor and -acceptor, respectively. For DiI- and DiO-entrapped solutions of P1, when mixed, no prominent FRET appeared even after 24 h. In sharp contrast, for P2, intense FRET emission occurred, and the FRET ratio (approximately 0.9) reached saturation in approximately 15 h, indicating the greatly enhanced kinetic stability of P1 aggregates. Glutathione-induced release of encapsulated Nile red showed much slower kinetics for P1 compared to that of P2, which was corroborated by the observed slow chain-exchange dynamics of the highly stable alternating copolymer assembly. Furthermore, the well-ordered assembly of P1 exhibited an excellent surface-functional group display (zeta potential of -32 mV compared to -14 mV for P2), which resulted in the effective recognition of the α-chymotrypsin (Cht) protein surface by electrostatic interaction. Consequently, P1 significantly (>70%) suppressed the enzymatic activity of Cht, while in the presence of P2, the enzyme was still active with >70% efficacy.

PH-Responsive self-assembled polymer-photosensitizer conjugate for activable photodynamic therapy.

This paper reports synthesis, aqueous self-assembly and relevance of the pH-triggered activable photodynamic therapy of amphiphilic polyurethane (P1S) functionalized with a heavy-atom free organic photosensitizer. Condensation polymerization between 1,4-diisocyanatobutane and two different dihydroxy monomers (one having a pendant hydrophilic wedge and the other having 1,3-dihydroxypropan-2-one with a reactive carbonyl group) in the presence of a measured amount of (S)-2-methylbutan-1-ol (chain-stopper) and DABCO catalyst produces a reactive pre-polymer P1. Hydrazide-functionalized thionated-naphthalenemonoimide (NMIS), which acts as a photosensitizer, reacted with the carbonyl-functionality of P1 to obtain the desired polymer-photosensitizer conjugate P1S in which the dye was attached to the polymer backbone via an acid-labile hydrazone linker. In water, P1S adopted an intra-chain H-bonding stabilized folded structure, which further assembled to produce a polymersome structure (Dh ≈ 200 nm), in which the hydrophobic membrane consists of aggregated NMIS and trialkoxy-benzene chromophores, as evident from UV/vis, CD and small-angle X-ray diffraction studies. In the aggregated state, NMIS loses its reactive oxygen species (ROS) generation ability and remains in a dormant state. However, under acidic conditions (pH 5.5), the photosensitizer is detached (presumably because of the cleavage of the hydrazone linker) and regains its full ROS-generation activity under photoirradiation, as evidenced from the standard DCFH assay. To test the possibility of such pH-activable intra-cellular ROS generation, P1S was treated with HeLa cells, as it is known that cancer cells are more acidic than normal cells. Indeed, photoirradiation-induced intra-cellular ROS generation was evident by the DCFH assay, resulting in efficient cell killing.

Design of biodegradable polyurethanes and post-modification with long alkyl chains via inhibiting biofilm formation and killing drug-resistant bacteria for the treatment of wound bacterial infection.

The development of cationic polymers that simulate antimicrobial peptides to treat bacterial infections has received much research interest. In order to obtain polymers that can not only eradicate bacteria but also inhibit biofilm formation, without inducing bacterial drug resistance, a series of cationic polymers have been developed. Despite recent progress, the chemical structures of these polymers are stable, making them recalcitrant to biodegradation and metabolism within organisms, potentially inducing long-term toxicity. To overcome this limitation, herein, a novel strategy of designing biodegradable polyurethanes with tertiary amines and quaternary ammonium salts via condensation polymerization and post-functionalizing them is reported. These polymers were found to exhibit potent antibacterial activity against Staphylococcus aureus and Escherichia coli, effectively prevent the formation of Staphylococcus aureus biofilms, act quickly and effectively against bacteria and display no resistance after repeated use. In addition, the potent in vivo antibacterial effects of these antimicrobial polyurethanes in a mouse model with methicillin-resistant Staphylococcus aureus skin infection are demonstrated.