Different Degrees Of Grafting Research Articles

Hydrodynamic alignment and self-assembly of cationic lignin polymers made of architecturally altered monomers

Cationic kraft lignin (CKL) polymers with different degrees of grafting (35.2–125.5 mol%) were synthesized via polymerizing kraft lignin (KL) and [2-(acryloyloxy)ethyl]trimethylammonium chloride (ATAC) or [2 (methacryloyloxy)ethyl]trimethylammonium methyl sulfate (METAM) to investigate the impact of the chain extension of the polymers on the physicochemical behavior of CKL in an aqueous solution. It was observed that, at the same grafting ratio, the structural difference of CKLs influenced their hydrophilicity, in which the contact angle of KL-METAM and KL-ATAC solution (1 g/L) reached 9.4° and 11.8° on a glass slide, respectively, at the maximum degree of grafting of ~125 mol%. KL-METAM had a more three-dimensional and flexible structure than KL-ATAC in solution, which promoted its self-assembly (with the aggregate diameter of 235–532 nm) and sedimentation (with the TSI value of 16.8). The rheological studies confirmed the more elasticity of KL-METAM than KL-ATAC with the elastic modulus of 9.3 and 8 Pa at the highest frequency. Quartz crystal microbalance (QCM) adsorption studies illustrated that KL-METAM adsorbed more greatly and generated a bulkier and more viscoelastic adlayer than KL-ATAC did on a rigid surface, below saturation (ΔD/Δf slope of 0.13–0.45) and at equilibrium (ΔD/Δf slope of 0.02–0.17). For the deposited adlayer, the alterations in the slope of dissipation/frequency (ΔD/Δf) between the early and late stages of adsorption were claimed to be related to the conformational changes of CKLs upon adsorption. The findings of this study showed that the architecture of cationic monomers could affect the structure of CKLs so significantly that the lignin polymers would have different chain conformations and flexibility in solution, varied rheological properties, and adsorption performance on a solid surface. The significance of the monomer architecture on the properties and performance of CKLs was more observable at a higher grafting ratio.

Enhanced Proton Conductivity of Porous UHMWPE membrane with Graphene-based material for Vanadium Redox Flow Battery

Porous membrane with enhanced proton conductivity is designed and prepared for vanadium redox flow battery (VRFB). The membrane is composed of ultra height molecular weight polyethylene (UHMWPE) grafted with poly(vinylbenzyl chloride) (PVBC) at different degrees of grafting (DOG). Subsequently, the membrane is functionalized with graphene oxide (UHMWPE-g-PVBGO) under ultrasonication. The functionalization of the GO on the porous substrates is confirmed by Fourier transform infrared (FTIR) and Raman analyses. UHMWPE-g-PVBGO membranes exhibited ∼37% higher proton conductivity compared to pristine UHMWPE upon modification at 30 °C and 100% relative humidity (RH). In relation to the degree of grafting, a higher degree of grafting possessed higher proton conductivity value for the porous membrane.

EFFECTS OF VISCOELASTIC PROPERTIES AND HYDRATION KINETIC ON DRUG RELEASE FROM THE TABLET OF DICLOFENAC SODIUM BASED ON POLY (SODIUM ACRYLATE)-GRAFTED-GELLAN MATRIX

Investigation of the effects of viscoelasticity and hydration kinetic on the drug release behavior from the poly (sodium acrylate)-grafted-gellan matrix (PSAc-g-GG) was the main objective of this study. At first, poly (acrylic acid)-grafted-gellan was treated with 0.05M NaOH to obtain poly (sodium acrylate)-grafted-gellan followed by its purification and subsequent lyophilicity study and viscoelastic study on PSAc-g-GG with different degree of grafting. The study revealed that the degree of grafting greatly affects the viscoelastic and rheologic characteristics of the copolymer, which further affect the drug release profile from the polymeric matrix. The copolymer with highest grafting (626.3%) exhibited much higher starting % strain (17.79%), stress (53.7 Pa) for structural breakdown at Gꞌ = Gꞌꞌ (214.4 Pa), higher storage modulus (G’), much greater values of complex viscosity (11.5 Pa.s) and cross-over point (Gꞌ = Gꞌꞌ =271.65 Pa) compared to that of the batch of copolymer with lower grafting. The water uptake index (%WE) was found to be directly proportional to the percentage grafting (%G), whereas the batches with higher grafting revealed lower initial swelling rate representing its inversely proportional relation to %grafting in case of 0.1N HCl acid. Equilibrium swelling and hydration were also found to be proportional to % grafting. The similar effect was observed in phosphate buffer solution (pH 6.8) with an exception that the degree of the swelling parameters obtained from phosphate buffer was very much greater compared to that found in 0.1N HCl. PSAc-g-GG exhibited extended drug release over a period of 10 hours with the drug release mechanism based on Case-1 Fickian diffusion or square root of time kinetic. The study also exhibited the usefulness of viscoelastic and swelling study in order to identify the effects of the degree of grafting on the drug release.

PH-sensitive microfiltration membrane prepared from polyethersulfone grafted with poly(itaconic acid) synthesized by simultaneous irradiation in homogeneous phase.

Poly(itaconic acid) (PIA) was grafted onto polyethersulfone (PES) by homogeneously phased γ-ray irradiation. Kinetic polymerization observed was studied by analyzing the effect of irradiation dosages and monomer concentrations. Then, a pH-sensitive microfiltration (MF) membrane was prepared from these PES-g-PIA polymers with different degrees of grafting under phase inversion method. Finally, the contact angles, morphologies, pore sizes, deionized water permeability and filtration performance for aqueous polyethylene glycols solution of the MF membranes were studied. The results show that grafting PIA groups onto PES molecular chains endowed the MF membranes with effective pH-sensitive properties.

Indomethacin functionalised poly(glycerol adipate) nanospheres as promising candidates for modified drug release

The linear polyester poly(glycerol adipate) (PGA) with its free pendant hydroxyl groups was covalently grafted with indomethacin which yields polymeric prodrugs. It was possible to produce nanospheres with narrow particle size distribution of these polymer-drug conjugates with an optimized interfacial deposition method. Nanospheres were characterized by zeta potential measurements, dynamic light scattering, electron microscopy and nanoparticle tracking analysis. Moreover, cell viability studies and cytotoxicity tests in three different cell lines were carried out showing low toxicity for three different degrees of grafting. In addition, the nanospheres had (in contrast to the free drug) low hemolytic activity in vitro.Release studies of nanodispersions are challenging. The use of a specially developed setup with highly porous aluminum oxide membranes enabled us to overcome problems associated with other setups (e.g. dialysis membranes). A slow and controlled release profile without any burst was observed over 15 days. The results indicate that indomethacin-PGA conjugates can be formulated successfully as nanospheres with the desired characteristics of small size with narrow distribution, controlled drug release and low toxicity. The newly developed particles have the potential to improve the therapy of inflammation and associated diseases.

PH and thermal-dependent ultrafiltration membranes prepared from poly (methacrylic acid) grafted onto polyethersulfone synthesized by simultaneous irradiation in homogenous phase

Polyethersulfone (PES) and monomer methacrylic acid (MAA) were chosen to synthesize the grafted polymer PES-g-PMAA by simultaneous γ-ray irradiation in homogenous phase. Membranes prepared from pristine PES and PES-g-PMAA with different degrees of grafting (DGs), have been obtained. The kinetics of grafting reaction and the DG values were studied through sulphur elemental analysis. The morphology study of the membranes showed formation of sponge-like structure in the sub-layer of membrane, along with grafting PMAA onto the PES chains. By ultrafiltration experiments, a regular pH-dependent permeability and thermal-dependent permeability of PES-g-PMAA membranes was demonstrated through introduction of PMAA onto the PES which reduced the water flux of the membranes. The pH-dependent permeability could be attributed to pH-sensitive reconfiguration of PMAA molecule chains on the surface of membrane pore, while thermal-dependent permeability might be caused by better thermal-sensibility of PMAA chains inside the membrane.

Modification of UHMWPE porous fibers by acrylic acid and its adsorption kinetics for Cu2+ removal

Polyacrylic acid-grafted ultrahigh molecular weight polyethylene (UHMWPE-g-PAA) fibers were prepared by radiation-induced grafting of acrylic acid onto UHMWPE porous fibers and were examined for Cu2+ removal from aqueous solutions. The developed fibers were characterized using Fourier transform infrared spectroscopy, mechanics test, scanning electron microscopy and energetic dispersive spectroscopy analysis. It was demonstrated that the UHMWPE fibers were modified successfully with grafted acrylic acid, which conferred excellent hydrophilic performance to UHMWPE porous fibers. The mechanics test indicated that considerable mechanical strength (~0.4 GPa) still reserved for the UHMWPE-g-PAA fibers in spite of somewhat radiation degradation. The high-strength, hydrophilic and porous natures render UHMWPE-g-PAA fibers promising as economical adsorbent in wastewater treatment. Prepared under different radiation dose and different degree of grafting of polyacrylic acid (PAA), the adsorption kinetics of the UHMWPE-g-PAA fibers was investigated using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. The results reveal a large adsorption capacity of 63 mg g−1 for the UHMWPE-g-PAA fibers and the adsorption behavior follows perfectly a pseudo-second-order kinetics model regarding the Cu2+ solution adsorption.

Optimization of acrylic acid grafting onto polypropylene using response surface methodology and its biodegradability

Simultaneous radiation grafting was optimized to graft acrylic acid monomer on the polypropylene (PP) films to make them hydrophilic and enhance their biodegradability. Experiments were designed based on full factorial central composite design (response surface methodology) and influence of monomer concentration, radiation dose, inhibitor concentration, solvent concentration on degree of grafting was investigated. The extent of grafting was found to increase with increasing monomer concentration, inhibitor concentration and radiation dose. The targeted 35% grafting could be achieved at optimum condition viz. monomer concentration 12.09wt%, radiation dose 12.40 kGy, inhibitor concentration 0.07M and solvent concentration 0.12M. The grafted PP films at different degrees of grafting were tested for tensile properties and characterized by swelling studies, fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Successful grafting of acrylic acid onto polypropylene films was indicated by FTIR and confirmed quantitatively by determination of carboxylic groups on the film surface. Tensile strength of grafted PP films decreased with increase in degree of grafting. The crystallinity of the grafted PP films was lower than that of PP film as indicated by DSC studies. Grafting of acrylic acid increased the roughness on the surface of PP films indicated by SEM studies. The maximum biodegradability of the 34.55% grafted film was 5.5%.

Nanogels of methylcellulose hydrophobized with N-tert-butylacrylamide for ocular drug delivery.

While eye drops account for the majority of ophthalmic formulation for drug delivery, their efficiency is limited by rapid pre-corneal loss. In this study, we investigate nanogel suspensions in order to improve the topical ocular therapy by reducing dosage and frequency of administration. We synthesized self-assembling nanogels of 140nm by grafting side chains of poly(N-tert-butylacrylamide) (PNtBAm) on methylcellulose via cerium ammonium nitrate. Successful grafting of PNtBAm onto methylcellulose (MC) was confirmed by both NMR and ATR. Synthesized molecules (MC-g-PNtBAm) self-assembled in water driven by hydrophobic interaction of the grafted side chains creating colloid solutions. Materials were synthesized by changing feed ratios of acid, initiator and monomer in order to control the degree of hydrophobic modification. The nanogels were tested for different degrees of grafting. Viability studies performed with HCE cells testified to the biocompatibility of poly(N-tert-butylacrylamide) grafted methylcellulose nanogels. Dexamethasone was entrapped with an efficiency superior to 95% and its release presented minimal burst phase. Diffusion of drug from the nanogels was found to be delayed by increasing the degree of grafting. The release profile of the entrapped compound from the MC-g-PNtBAm nanogels can thus be tuned by simply adjusting the degree of hydrophobic modification. MC-g-PNtBAm nanogels present promising properties for ocular drug delivery.

Radiation-induced grafting of acrylic acid onto polypropylene film and its biodegradability

Abstract Polypropylene based commodity polyolefins are widely used in packaging, manufacturing, electrical, pharmaceutical and other applications. The aim of the present work is to study the effect of grafting of acrylic acid on the biodegradability of acrylic acid grafted polypropylene. The effect of different conditions showed that grafting percentage increased with increase in monomer concentration, radiation dose and inhibitor concentration but decreased with increase in radiation dose rate. The maximum grafting of 159.4% could be achieved at optimum conditions. The structure of grafted polypropylene films at different degree of grafting was characterized by EDS, FTIR, TGA, DSC, SEM and XRD. EDS studies showed that the increase in acrylic acid grafting percentage increased the hydrophilicity of the grafted films. FTIR studies indicated the presence of acrylic acid on the surface of polypropylene film. TGA studies revealed that thermal stability decreased with increase in grafting percentage. DSC studies showed that melting temperature and crystallinity of the grafted polypropylene films lower than polypropylene film. SEM studies indicated that increase in acrylic acid grafting percentage increased the wrinkles in the grafted films. The maximum biodegradability could be achieved to 6.85% for 90.5% grafting. This suggested that microorganisms present in the compost could biodegrade acrylic acid grafted polypropylene.

Phenylboronic acid functionalized methylcellulose based nanogels as mucoadhesive ocular drug delivery system

Event Abstract Back to Event Phenylboronic acid functionalized methylcellulose based nanogels as mucoadhesive ocular drug delivery system Marion Jamard1 and Heather Sheardown1, 2 1 McMaster University, School of Biomedical Engineering, Canada 2 McMaster University, Department of Chemical Engineering, Canada Introduction: The interaction between drug carrier and precorneal mucin plays an important role in precorneal drug absorption and depends on the functionality and the charges of the carriers. We recently synthesized a copolymer made of methylcellulose hydrophobized with poly(N-tert-butylacrylamide), MC-g-PNtBAm, that self-assembles in aqueous media to form nanogels[1] of 140 nm in diameter. We postulate that the methylcellulose on the surface on the MC-g-PNtBAm nanogels can be modified to target the ocular surface, and thus prolong corneal retention. Increasing the residence time of the drug in the precorneal area would prolong the penetration of the drug into the intraocular structures, making it suitable the ophthalmic application[2]. Phenylboronic acid (PBA) contains a phenyl substituent and two hydroxyl groups attached to boron which can form a complex with the diol groups of sialic acid at physiological pH. In this study, we are aiming at functionalizing the MC-g-PNtBAm nanogel surfaces with PBA molecules for specific targeting of sialic acid residues of the ocular mucosa. Methods: MC-g-PNtBAm nanogels were synthesized by grafting chains of poly(N-tert-butylacrylamide) onto methylcellulose via cerium ammonium nitrate. Cytocompatibility was assessed on human cornel epithelium cells (hCECs) by MTT assay and live/dead assay. Release of dexamethasone was examined and quantified by high-performance liquid chromatography (HPLC). To functionalize the surface with PBA, a Schiff base reaction between the primary amine groups of the PBA and the carbonyl groups on the MC polymer chain was performed. To generate a reactive MC support, MC is oxidized with sodium m-periodate. PBA grafting was verified by nuclear magnetic resonance (NMR), attenuated total reflectance (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The morphology of the nanogels will ultimately be studied via transmission electron microscopy (TEM). Results: The nanogels were tested for different degrees of grafting. After incubating for 48h, the relative cell viability was higher than 90% for all of the nanogels, indicating that their presence did not negatively impact cell viability. The MTT assay testified of no negative effect on the metabolism. Dexamethasone was entrapped with an efficiency superior to 95% and its release presented minimal burst phase. Diffusion of drug from the nanogels was found to be delayed by increasing the degree of grafting. The release profile of the entrapped compound from the MC-g-PNtBAm nanogels can thus be tuned by simply adjusting the degree of hydrophobic modification. NMR confirmed successful grafting of PBA with peaks in the 6.5-8 ppm range corresponding to the phenyl ring and amine of PBA. ATR-FTIR showed peaks at 1651 cm-1, 1566 cm-1, 1346 cm-1 corresponding to the C=O, N-H and B-O groups respectively. The presence of boron was also confirmed by XPS. TEM proved that the nanogels kept their spherical morphology after functionalization of the nanogels and indicated that their size in dry state increased with PBA grafting. Conclusion: Viability studies performed with HCE cells testified to the biocompatibility of poly(N-tert-butylacrylamide) grafted methylcellulose nanogels. As well the synthesized nanogels showed efficient entrapment of dexamethasone. The drug presented no significant burst phase and was released slowly over several weeks, with a release rate that was tunable with the degree of grafting. The surface of the nanogels of MC-g-PNtBAm was successfully modified with PBA. The nanogels retained their spherical morphology after functionalization. The current study provides promising results for the potential use of MC-g-PNtBAm nanogels to improve the bioavailability of ocular drugs intended to target the anterior segment of the eye. Further experiments will investigate the impact of PBA grafting on drug release and mucoadhesion. Dr Jianfeng Zhang; Prof Todd Hoare; CREATE Biointerfaces Training Program; Natural Sciences and Engineering Research Council of Canada (NSERC)

PEGylated chitosan microspheres as mucoadhesive drug‐delivery carriers for puerarin

ABSTRACTPEGylated chitosans with different degrees of grafting were synthesized, and the application potential of microspheres based on PEGylated chitosan as mucoadhesive drug‐delivery carriers for puerarin was investigated. Compared with chitosan microspheres, PEGylated chitosan microspheres (PCMs) exhibited better physical stability and higher swelling capacity, and the amount of water uptake increased as the content of poly(ethylene glycol) methyl ether in the microspheres increased. PCMs showed obviously improved mucoadhesive behavior on a mucosa‐like surface. Puerarin was incorporated into the microspheres, and the release experiments in vitro showed that the PEGylation of chitosan accelerated puerarin release from the particles and decreased the retention of the drug. The abilities of all of the tested microspheres to open tight junctions and improve the permeability of puerarin were demonstrated with a Caco‐2 cell monolayer as an in vitro model. The amount of puerarin permeating across the Caco‐2 cell monolayer was significantly increased by the incorporation of puerarin into the PCMs. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42623.

Radiochemical Graft Copolymerization and Characterization of Acrylate Monomers on to Polyethylene Film

Functionalization of polyethylene (PE) film by radiation-induced graft copolymerization of ethyl acrylate (EA) and ethyl methacrylate (EMA) has been carried out using a preirradiation technique to develop materials with different degrees of grafting for use in ion separation processes. The influence of reaction conditions such as preirradiation dose, monomer concentration, reaction time and amount of solvent on percentage of grafting (Pg) has been studied and maximum Pg values of EA (144.97%) and EMA (142.35%) were respectively obtained at [EA] = 0.92 mol/L, [EMA] = 0.80 mol/L, total dose = 14.4 kGy and 17.28 kGy at 100 °C in 120 and 180 min. The effect of different monohydric alcohols of varying chain lengths on Pg has also been studied. The modified films have been characterized by FTIR, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods. Some selective properties of pristine and grafted PE film such as swelling and ion uptake studies have also been investigated. The grafted films showed better swelling and ion uptake capacity in comparison to the pristine film.

Long-term durability of radiation-grafted PFA-g-PSSA membranes for direct methanol fuel cells

Poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether)-graft-poly(styrene sulfonic acid) (PFA-g-PSSA) membranes were prepared by γ-ray radiation-induced grafting of styrene onto 50μm PFA films and a subsequent sulfonation. The properties of the PFA-g-PSSA membranes such as ion exchange capacity, water uptake, proton conductivity, and methanol permeability were evaluated and compared with commercial Nafion 115 membrane. The characteristic properties and direct methanol fuel cell (DMFC) performances with PFA-g-PSSA membrane were better than that with the Nafion 115 membrane. The power density of the single cell with PFA-PSSA30, PFA-PSSA50, PFA-PSSA80 membranes having different degree of grafting (DOG), and Nafion 115 membranes was 113, 123, 118, and 111mWcm−2 at 0.4V, respectively. To study the long-term durability of the prepared membrane electrode assembly (MEA) with a PFA-PSSA50 membrane, the single cell was tested for 2066h in a galvanostatic mode under a constant load 150mAcm−2 and at a temperature of 60°C. The performance loss of the MEA after 2066h operation was about 26.8%. Before and after the long-term performance test, the degradation of MEA with PFA-g-PSSA membrane was investigated by polarization curve technique, electrochemical impedance spectroscopy, TEM, X-ray diffraction, and ion exchange capacity.

Microfiltration membranes prepared from poly(N-vinyl-2-pyrrolidone) grafted poly(vinylidene fluoride) synthesized by simultaneous irradiation

Poly(N-vinyl-2-pyrrolidone) grafted poly(vinylidene fluoride) (PVDF-g-PVP) copolymers were synthesized by a simultaneous irradiation induced graft polymerization technique in a homogeneous system. The kinetics of the radiation induced graft polymerization was studied. Evidence for the existence of the graft chains in grafted PVDF was characterized by FT-IR spectroscopy in ATR mode. Then, membranes were cast from pristine PVDF and PVDF-g-PVP of different degree of grafting (DG) under phase inversion method. The contact angle, water uptake, water filtration and antifouling property of membranes were measured. The morphology was also studied with the use of AFM and SEM. The results showed that with the increasing DG, the contact angle became smaller, the water uptake, RMS roughness, water flux and pore size and amount of the membrane surface increased. The water flux recovery showed that membranes cast from PVDF-g-PVP also possessed an effective antifouling performance.

Design and Photonic Properties of Novel Fluorinated Copolymers Bearing Phthalocyanine Side Groups

The design and characterization of amorphous alternating copolymers endowed with a satisfactory thermal stability are reported. These alternating poly(CTFE-alt-CEVE) copolymers are synthesized by radical copolymerization of chlorotrifluoroethylene (CTFE) with 2-chloroethyl vinyl ether (CEVE), which are first modified into poly[CTFE-alt-(2-iodoethyl vinyl ether)] copolymers and then azidated in high yields. Alkynyl CF3-containing phthalocyanines (Pcs) are then grafted via a copper-catalyzed Huisgen dipolar 1,3-addition (“grafting onto”), hence providing fluorinated copolymers with different degrees of grafting (from 10 to 72%) of Pc dangling groups. Electronic spectral (absorption, excitation, and fluorescence) and photophysical properties (fluorescence lifetimes, τF, and quantum yields, ΦF) are evaluated.

On the statistical physics modeling of dye adsorption onto anionized nylon: Consequent new interpretations

AbstractExperimental adsorption isotherm of two basic dyes: Basic Blue 3 and Basic Red 24 from aqueous solution onto modified nylon 6,6 were analyzed by using a double layer adsorption model with two energy levels. Such model is based on statistical physics treatment. The parameters involved in the analytical expression of this model such as the fraction or the number of adsorbed dye molecule(s) per site, n, the receptor sites density, NM, and the energetic parameters, c1 and c2, were determined by fitting the experimental adsorption isotherms at four temperatures between 293 and 353 K with different degrees of grafting between 20 and 80%. The evolution of these parameters versus temperature and the grafting percent allows us to interpret and better understand this adsorption process at molecular level. Two different behaviors of the two dye molecules were highlighted according to their localized and non localized charges. The configurational entropy at various temperatures has also been studied. This parameter allowed to deduce some results related to the evolution of the disorder at the adsorption surface. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

A study on the characterization of FEP-g-PVBSA membranes as polymer electrolytes for direct methanol fuel cells

Poly(vinylbenzyl sulfonic acid)-grafted poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP- g-PVBSA) electrolyte membrane was prepared by radiation-induced grafting of vinylbenzyl chloride onto FEP film with subsequent sulfonation processes. An energy dispersive X-ray analysis was used to observe the cross-sectional distribution behaviors of the hydrophilic sulfonic acid groups and hydrophobic fluorine groups. The characteristics of an ion-exchange capacity (IEC), water and methanol uptake, methanol permeability, and proton conductivity as a function of the degree of grafting were studied. The IECs and water uptakes of membranes with different degrees of grafting (36 to 102%) were measured in the range of 0.8 to 1.62 meq g−1 and 10 to 30%, respectively. The proton conductivity was higher than that of a Nafion 212 membrane (6.1 E−02 S cm−1), when the degree of grafting reached 60%. The methanol permeability and uptake of the FEP- g-PVBSA membrane was significantly lower than that of the Nafion 212 membrane, and even the degree of grafting reached 102%.

Effect of the degree of grafting in hydrophobically modified inulin polymeric surfactants on the steric forces in foam and oil-in-water emulsion films

The interaction forces in foam and oil-in-water emulsion films stabilized by four inulin based graft copolymers with different degree of grafting of the dodecyl chains onto the inulin backbone were investigated. The adsorbing copolymers were found to form inulin-loops at the oil (air)/water interface, as the inulin-loop size decreased with increasing degree of grafting. Disjoining pressure isotherms (disjoining pressure, Π vs. equivalent film thickness, h w) were measured for the foam and emulsion films at sufficiently high NaCl concentration, whereby there is no electrostatic interaction in the films. Under these conditions, the stabilization of the films is due to interaction between the two layers of inulin-loops at oil (air)/water film interfaces. Transition to a stable Newton black film in the disjoining pressure isotherm for the emulsion films was observed for all the copolymers and the transition pressure significantly decreased for the films from the copolymer with the smallest inulin-loops. The stability against rupture of the foam films decreased with reducing inulin-loop size. The de Gennes’ scaling theory for interaction between polymer ‘brushes’ was fitted to the experimental data for the foam films with the inulin-loops layer thickness as a fitting parameter. The results were interpreted on the basis of inulin-loop size induced changes of the steric forces in the foam and emulsion films.

Stimuli–responsive networks grafted onto polypropylene for the sustained delivery of NSAIDs

Co-polymers of N-isopropyl acrylamide (NIPAAm) and N-(3-aminopropyl) methacrylamide hydrochloride (APMA) were grafted on polypropylene (PP) films by means of a γ-ray pre-irradiation method, with the aim of developing medical devices able to load non-steroidal anti-inflammatory drugs (NSAIDs) and to control their release under physiological conditions. The NIPAAm/APMA molar ratios in the grafts, estimated by Fourier transform infrared attenuated total reflection spectroscopy and X-ray photoelectron spectroscopy analysis, were 4.76 and 1.23 for PP-g-(1M NIPAAm-r-0.5M APMA) and PP-g-(1M NIPAAm-r-1M APMA), respectively. By varying the reaction time, different degrees of grafting were achieved, while the monomer ratio was kept constant. PP-g-(NIPAAm-r-APMA) films showed temperature-responsive swelling, smaller friction coefficients, hemolysis and thrombogenicity and higher cell compatibility, did not elicit secretion of cytokines, and took up remarkable amounts of diclofenac and ibuprofen and sustained delivery for several hours in phosphate buffer, pH 7.4. Coating with carboxymethyl dextran of diclofenac-loaded PP-g-(NIPAAm-r-APMA) films caused a minor discharge of the drug but did not alter the drug release rate.