Amphiphilic Polymer Networks Research Articles

Synthesis and characterization of amphiphilic polymer networks based on acrylated poly(ϵ‐caprolactone) and N‐vinylpyrrolidone

AbstractNew amphiphilic polymer networks were synthesized by the free‐radical copolymerization of α,ω‐diacryl polycaprolactone (DAPCL) and N‐vinylpyrrolidone (NVP), which was initiated by 0.5% azobisisobutyronitrile at 70°C. The chemical structures of the networks were characterized by proton nuclear magnetic resonance spectrometry. The NVP/DAPCL feed ratio played an important role in the crosslinking process. The synthesized amphiphilic polymer networks exhibited controlled swelling properties in water and organic solvents (ethanol, acetones, and toluene). A porous structure was observed for the amphiphilic polymer networks under a scanning electron microscope. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Unusual, Promoted Release of Guests from Amphiphilic Cross-Linked Polymer Networks

Hyperbranched fluoropolymer-poly(ethylene glycol) (HBFP-PEG) cross-linked networks have been found to exhibit capabilities for the encapsulation of high levels of geraniol guest molecules coupled with unusually rapid release of the volatile compound. The promotion of the release of the volatile fragrance geraniol, observed as decreasing volatilization temperatures and increasing volatilization rates by thermogravimetric analyses, was found to be dependent upon the HBFP-PEG network composition, with increasing effects from decreasing wt % PEG and a maximum effect occurring at 5 wt % PEG.

Interpenetrating Amphiphilic Polymer Networks of Poly(2-hydroxyethyl methacrylate) and Poly(ethylene oxide)

Interpenetrating polymer networks of poly(2-hydroxyethyl methacrylate) and poly(ethylene oxide) were synthesized by the free radical copolymerization of 2-hydroxyethyl methacrylate and ethylene glycol dimethacrylate in aqueous solutions of poly(ethylene oxide) diglycidyl ether (PEODGE), followed by amine−epoxy coupling reactions within the resultant gel network. The effects of ethylenediamine and PEODGE concentrations and coupling methods were examined and are discussed in this paper. Swelling studies and cryogenic-SEM analysis showed that these novel networks have high water intakes (equilibrium water content >3) and pore sizes on the order of up to 1 μm.

Synthesis of new amphiphilic and lypophilic polymer networks containing 2‐methyl‐ and 2‐nonyl‐2‐oxazoline by the macroinitiator method

AbstractNew amphiphilic and lypophilic polymer networks were obtained by the copolymerization of 2‐methyl‐2‐oxazoline (MeOXA), and/or 2‐nonyl‐2‐oxazoline (NoOXA) and 2,2′‐tetramethylenebis(2‐oxazoline) (BisOXA), respectively, initiating the copolymerization by random copolymers of chloromethylstyrene and methyl methacrylate or of chloromethylstyrene and styrene (macroinitiator method). Potassium iodide was used as an activator agent and the reaction was carried out in benzonitrile at 110 °C. In general, the polymer gels were obtained with a yield of 62 to 88%. The networks were characterized by high‐resolution magic angle spinning (HRMAS) NMR spectroscopy and by its absorption of polar and nonpolar solvents. In the case of amphiphilic polymer networks, the absorption of solvents depends on the molar ratio of 2‐methyl‐ to 2‐nonyl‐2‐oxazoline inside the polymer network favoring the absorption of polar solvents with a higher content of 2‐methyl‐2‐oxazoline. These gels showed a maximal swelling degree of 13 mL of water, 20 mL of methanol, and 13 mL of chloroform, respectively, per g of polymer. The lypophilic polymer networks containing only 2‐nonyl‐2‐oxazoline showed a maximal swelling degree of 8 mL of toluene, 14 mL of chloroform, and 2 mL of methanol, respectively, per g of the lypophilic network. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 122–128, 2005

Amphiphilic particulate phase semi-interpenetrating polymer networks based on recycled rubber matrix

The goal of this study is to enable the utilization of recycled rubber particles in aqueous media by producing amphiphilic particulate phase semi-interpenetrating polymer networks (PPSIPNs). Rubber granulates obtained from post-consumer rubber items were pulverized into fine particles using a solid state shear extrusion (SSSE) process. Reaction mixtures composed of toluene, acrylic acid (AA) monomer and azobisisobutyronitrile (AIBN) as an oil-soluble initiator were prepared and used to impregnate the produced rubber particles. Toluene was added as a co-swelling agent to induce more swelling of the rubber particles and, consequently, enhancement in the absorption of AA in the rubber network. The swollen particles were introduced into a micro-domain suspension polymerization reactor where the ionic strength of the aqueous phase was sufficient to prevent desorption of AA from the particles during the reaction. This resulted in formation and interpenetration of hydrophilic poly(acrylic acid) in the intermolecular structure of hydrophobic rubber network. The resulting composite particles are water dispersible and suitable for use in a variety of aqueous applications such as, additives to waterborne emulsions and vehicles for wastewater treatment.

Amphiphilic and hydrophobic surface patterns generated from hyperbranched fluoropolymer/linear polymer networks: Minimally adhesive coatings via the crosslinking of hyperbranched fluoropolymers

AbstractHyperbranched fluoropolymers (HBFPs), based on benzyl ether linkages and having a large number of pentafluorophenyl chain ends, were crosslinked by a reaction with diamino‐terminated poly(ethylene glycol) (PEG) or diamino‐terminated poly(dimethyl siloxane) (PDMS) to form hyperbranched–linear copolymer networks of different compositions, structures, and properties. The crosslinking reactions involved the nucleophilic aromatic substitution of the pentafluorophenyl para‐fluorines of HBFP by the amine functionalities of the respective telechelic linear segments. The contact angles, differential scanning calorimetry, thermogravimetric analysis, tensile measurements, and atomic force microscopy (AFM) were used to characterize the resulting network film samples. The surface wettability of the crosslinked materials was affected by the nature and amount of the linear polymer crosslinking agent employed. Amphiphilic polymer networks were formed by the incorporation of diamino‐terminated PEG as a crosslinker, whereas diamino‐terminated PDMS produced polymer networks of a hydrophobic character. The mechanical properties improved upon crosslinking, as measured by tensile testing. The mechanical integrity of the films was also found to improve upon crosslinking, as measured by AFM machining protocols. The AFM images revealed topographical morphologies that appeared to be the result of phase segregation of HBFP from PEG or PDMS; the dimensions of the phase‐segregated domains were dependent on the stoichiometry of HBFP to the linear polymer and the thickness of the coating. As the content of PEG increased, fouling by human fibrinogen, used as a model protein, decreased. Further studies are in progress to determine the effects of the surface composition, morphology, and topography on the biofouling characteristics. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3531–3540, 2003

Amphiphilic segmented polymer networks based on poly(2-alkyl-2-oxazoline) and poly(methyl methacrylate)

Amphiphilic segmented polymer networks (SPNs) have been prepared by free radical copolymerization of methyl methacrylate with α,ω-bisacrylate terminated poly(2-methyl-2-oxazoline) and poly(2-ethyl-2-oxazoline). DSC and DMTA analysis demonstrated the influence of the copolymer composition, the molecular weight and nature of the poly(2-alkyl-2-oxazoline)s and the polymerization conditions on the final phase morphology of the networks. A comparative phase morphology study of the polymer blends and SPNs revealed the more compatible phase morphology of the networks. The compatibility could be further increased by UV-induced network formation. The investigation of the solvent uptake in different solvents clearly demonstrated the amphiphilic nature of the SPNs.

Positronium as a tool to monitor changes of chemical structure

Abstract The applicability of positron annihilation spectroscopy for chemical structural problems is demonstrated by two examples: For the swelling dynamics of an amphiphilic polymer network, very quick structural changes were indicated by positronium lifetime parameters at very low swelling ratios and a hydration mechanism was proposed accordingly. For the series [Fe x Zn 1− x (propyltetrazole) 6 ](BF 4 ) 2 ( x =1, 0.6, 0.4, 0.1, 0), changes in the dynamic structure were revealed by positronium lifetime spectroscopy. For compounds of x >0, temperature-induced spin-crossover was detected.

Polymer Networks with Lamellar Structure

The lamellar liquid crystalline phase of a pentaethylene glycol monododecyl ether (C12E5)/decane/water system is used as a matrix to create amphiphilic polymer network structures from α,ω-hydrophobically modified poly(oxyethylenes) bearing polymerizable end groups and hydrophobic comonomers. The polymer networks preserve the characteristic layer structure and the orientation of the liquid crystalline phase even after extraction of the templating matrix. This allows the preparation of highly anisotropic polymer gels from magnetic field aligned liquid crystalline phases. The changes of the macroscopic dimensions and the layer spacings of the polymer network structure upon swelling these systems in a selective solvent, like water, are strongly correlated. The influence of the molecular weight of the bridging poly(oxyethylene) chains on the equilibrium swelling of the samples is investigated.

Structure of w/o-microemulsion templated polymer networks

The droplet phase of a water-in-oil microemulsion is used as a matrix to create amphiphilic polymer network structures from a poly(oxyethylene)-poly(isoprene)-poly(oxyethylene) triblock copolymer bearing polymerizable methacrylate end groups. Conductivity measurements and freeze fracture electron microscopy are used to obtain information about the structure of these gels. The droplet structure of the underlying microemulsion is only preserved for low droplet and polymer concentration. For higher concentrations the crosslinking reaction can induce the formation of a bicontinuous structure.

Water absorption in a polymeric network

Positron lifetime measurements were performed to study the swelling dynamics of an amphiphilic polymer network (APN). Lifetime spectroscopy proved to be suitable to investigate APNs. Very quick structural changes were indicated by lifetime parameters at very low swelling ratios. On the basis of the results a possible mechanism is proposed for the hydration of the investigated materials.

Structured Polymer Networks from O/W-Microemulsions and Liquid Crystalline Phases

The droplet and the lamellar liquid crystalline phase of a pentaethylene glycol monodocecyl ether (C12E5)/decane/water system is used as a matrix to create new amphiphilic polymer network structures from α,ω-hydrophobically modified poly(oxyethylene) bearing polymerizable end groups and hydrophobic comonomers. The influence of the individual “subnetworks” on the structure and phase behavior of the system is discussed. The fraction of bridge- and loop-forming polymer chains as a function of the droplet concentration in the system can be estimated from mechanical data. The number of bridges decreases considerably below a certain threshold concentration corresponding to the root-mean-square end-to-end distance of the poly(oxyethylene) chains.