Synthesis and characterization of poly (n-butyl acrylate)-poly (methyl methacrylate) latex interpenetrating polymer networks by radiation-induced seeded emulsion polymerization

A series of latex interpenetrating polymer networks (LIPNs) were prepared via a two-stage emulsion polymerization of methyl methacrylate (MMA) or mixture of MMA and n-butyl acrylate (n-BA) on crosslinked poly(n-butyl acrylate)(PBA) seed latex using ⁶⁰Co γ-ray radiation. The particles of resultant latex were produced with diameters between 150 and 250 nm. FTIR spectra identified the formation of crosslinked copolymers of PMMA or P(MMA-co-BA). Dynamic light scattering (DLS) showed that with increasing n-BA concentration in second-stage monomers, the particle size of LIPN increased. Transmission electron microscope(TEM) photographs showed that the morphology of resultant acrylate interpenetrating polymer network (IPN) latex varied from the distinct core-shell structure to homogenous particle structure with the increase of n-BA concentration, and the morphology was mainly controlled by the miscibility between crosslinked PBA seed and second-stage copolymers and polarity of P(MMA-co-BA)copolymers. In addition, differential scanning calorimeter (DSC) measurements indicated the existence of reinforced miscibility between PBA seed and P(MMA-co-BA)copolymer in prepared LIPNs.     

pH‐Modulating Poly(ethylene glycol)/Alginate Hydrogel Dressings for the Treatment of Chronic Wounds

The development of chronic wounds has been frequently associated with alkaline pH values. The application of pH‐modulating wound dressings can, therefore, be a promising treatment option to promote normal wound healing. This study reports on the development and characterization of acidic hydrogel dressings based on interpenetrating poly(ethylene glycol) diacrylate/acrylic acid/alginate networks. The incorporation of ionizable carboxylic acid groups results in high liquid uptake up to 500%. The combination of two separate polymer networks significantly improves the tensile and compressive stability. In a 2D cell migration assay, the application of hydrogels (0% to 1.5% acrylic acid) results in complete “wound” closure; hydrogels with 0.25% acrylic acid significantly increase the cell migration velocity to 19.8 ± 1.9 µm h⁻¹. The most promising formulation (hydrogels with 0.25% acrylic acid) is tested on 3D human skin constructs, increasing keratinocyte ingrowth into the wound by 164%.

     

蓖麻油TDI聚氨酯互穿网络的热降解

互穿网络聚合物;蓖麻油;聚氨酯;甲苯二异氰酸酯;热降解     

Photomechanical Switching Behavior of Semi‐Interpenetrating Polymer Network Consisting of Azobenzene‐Carrying Crosslinked Poly(vinyl ether) and Polycarbonate

Summary: A novel semi‐interpenetrating polymer network (semi‐IPN) with photomechanical switching ability was developed by a cationic copolymerization of azobenzene‐containing vinyl ethers in a matrix of a linear polycarbonate (PC). The semi‐IPN film showed reversible deformation upon switching the UV irradiation on and off and responded with unprecedented rapidity. The photomechanical effect is attributed to a reversible change between the highly aggregated and dissociated states of the azobenzene groups.

The reversible UV response of the length of the semi‐IPN film at 25 °C.     

A twofold interpenetrating three‐dimensional CdII coordination framework: poly[[μ2‐1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene](μ3‐5‐nitrobenzene‐1,3‐dicarboxylato)cadmium(II)]

A twofold interpenetrating three‐dimensional Cd^II coordination framework, [Cd(C₈H₃NO₆)(C₁₄H₁₄N₄)]_n, has been prepared and characterized by IR spectroscopy, elemental analysis, thermal analysis and single‐crystal X‐ray diffraction. The asymmetric unit consists of a divalent Cd^II atom, one 1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene (1,3‐BMIB) ligand and one fully deprotonated 5‐nitrobenzene‐1,3‐dicarboxylate (NO₂‐BDC²⁻) ligand. The coordination sphere of the Cd^II atom consists of five O‐donor atoms from three different NO₂‐BDC²⁻ ligands and two imidazole N‐donor atoms from two different 1,3‐BMIB ligands, forming a distorted {CdN₂O₅} pentagonal bipyramid. The NO₂‐BDC ligand links three Cd^II atoms via a μ₁‐η¹:η¹ chelating mode and a μ₂‐η²:η¹ bridging mode. The title compound is a twofold interpenetrating 3,5‐connected network with the {4².6⁵.8³}{4².6} topology. In addition, the compound exhibits fluorescence emissions in the solid state at room temperature.     

Synthesis,structure and luminescence properties of two new acylamide metal–organic frameworks showing 4‐connected CdSO4 and a threefold interpenetrating dia net

Two new acylamide metal–organic frameworks (MOFs), based on mixed N‐ and O‐donor ligands, with 4‐connected topologies have been obtained, namely poly[[μ₂‐N¹,N⁴‐bis(pyridin‐3‐yl)terephthalamide]bis(μ₃‐4,4′‐oxydibenzoato)dizinc(II)], [Zn₂(C₁₄H₈O₅)₂(C₁₈H₁₄N₄O₂)]_n, (1), and poly[[(μ₂‐benzene‐1,4‐dicarboxylato)[μ₂‐N⁴,N^4′‐bis(pyridin‐3‐yl)‐[1,1′‐biphenyl]‐4,4′‐dicarboxamide]dicadmium(II)] dihydrate], {[Cd(C₈H₄O₄)(C₂₄H₁₈N₄O₂)]·2H₂O}_n, (2). Complex (1) is a 4‐connected CdSO₄ net with no interpenetration, where the Zn^II cation is regarded as a 4‐connecting node with square geometry. Complex (2) is a 4‐connected dia net with threefold interpenetration, where the Cd^II cation acts as a 4‐connecting node with tetrahedral geometry. The results of thermogravimetric and luminescence analyses are described in detail.     

Damping,Thermal, and Mechanical Properties of Polycaprolactone-Based PU/EP Graft IPNs: Effects of Composition and Isocyanate Index

A series of polycaprolactone (PCL)-based polyurethane (PU)/epoxy resin (EP) graft interpenetrating polymer networks (IPNs) were prepared and their damping propertiesand thermal stability, as well as mechanical properties, were systematically studied in terms of composition and the values of the PU isocyanate index (R). The morphologies of the PU/EP IPNs were observed by scanning electron microscope (SEM) and atomic force microscope (AFM) characterization and the relationship between the morphologies and the properties is also discussed. The damping properties and thermal stability measurements revealed that the formation of PU/EP IPNs could significantly improve not only the damping properties but also the thermal stability. Meanwhile, the mechanical tests showed that the tensile strengths of the IPNs decreased, while their impact strengths increased with increasing PU content. The value of the PU isocyanate index also had significant impacts on the properties of the IPNs when the PU to EP ratio was fixed, which could be an effective means for manipulating the fabrication of PU/EP IPNs. From the results obtained, the PCL-based PU/EP IPNs hold promise for use in structural damping materials.     

Effect of new hyperbranched polyester of varying generations on toughening of epoxy resin through interpenetrating polymer networks using urethane linkages

In this study, a previously unreported methodology is attempted to improve the inherent brittleness in diglycidyl ether of bisphenol-A based epoxy resin using hyperbranched polymers as toughening agents. Four different hyperbranched polyesters (HBPs) with increasing generations (1–4, denoted as HBP-G1 to HBP-G4) were synthesized by reacting calculated amount of dipentaerythritol (used as a core) and dimethylol propionic acid (AB₂ type monomer) through pseudo one-step melt polycondensation method. The newly synthesized HBPs were characterized using spectral, thermal and physical measurements, which confirmed the formation of highly branched structure and decreasing thermal stability with increasing HBP generations. Further, toughening of the epoxy resin is carried out by reacting each generation of the HBP with epoxy using hexamethylene diisocyanate as an intermediate linkage resulting in the formation of HBP-Polyurethane/Epoxy-g-Interpenetrating Polymer Networks (HBP-PU/EP-g-IPNs). A linear polyol-PU/EP-g-IPN is also synthesized for the purpose of comparison. It is found that the HBP modified epoxy samples exhibited higher toughness in comparison to that of neat epoxy and linear polyol based epoxy samples. On the other hand, flexural properties, thermal stability and glass transition temperature of the modified samples is lower than neat epoxy sample due to the existence of flexible urethane linkages and decrease in the cross-linking density of epoxy matrix. The toughening characteristics exhibited by the HBPs are corroborated from the existence of heterogeneous morphology using SEM data.     

Gas transport in polyurethane-polystyrene interpenetrating polymer network membranes. I. Effect of synthesis temperature and molecular structure variation

The gas (oxygen and nitrogen) transport characteristics of the interpenetrating polymer network (IPN) membranes of polyurethane/polystyrene were studied. The effect of synthesis temperature, composition, molecular weight of the polyol and aromatic content (of MDI, TDI and HDI) on the gas permeability were analyzed. In the IPN synthesis, first polyurethane was polymerized thermally, and then polystyrene was polymerized by photolytic methods at different temperatures. The permeability coefficient decreased and the separation factor increased with decreasing synthesis temperature due to the miscibility increase. The permeability coefficient showed a minimum value and the separation factor showed a maximum value at ca.25 wt.% polyurethane composition. The permeability coefficient decreased and the separation factor increased with increasing aromatic content in polyurethane component. The morphology and density behavior of the IPN's agreed well with the permeability data. The tensile strength of the membrane increased with decreasing synthesis temperature and with increasing crosslink density and polystyrene content.