Search

High-density polyethylene HDPE is a highly polluting plastic, and its reuse, reprocessing and modification are subjects of current research to mitigate environmental pollution. In recent times, it has been modified for specialized purposes as a harmless and resistant polymer. The present work details the modification of HDPE (obtained from Bonafont, Coke, and Gatorade caps) with the monomer 4-vinylpyridine (4VP) via radiation-induced grafting copolymerization initiated by gamma rays from a Co-60 source and with the subsequent Ag(I) loading using the reagent AgNO3 in aqueous medium. Poly(4VP) is widely used to retain metals and manufacture pH-responsive polymers, while Ag(I) is a recognized bactericide harmless to humans at therapeutic concentrations; therefore, both poly4VP and Ag(I) can work in a synergistic system against pathologic bacteria as is here proposed. We advance a favorable antimicrobial activity of the Ag-loaded graft copolymers evaluated in vitro with Kirby-Bauer tests against Pseudomonas aeruginosa and Staphylococcus aureus. Additionally, FTIR-ATR, TGA, contact angle, swelling, and pH response were carried out to complete the characterization. [ABSTRACT FROM AUTHOR]

The functionalization of polymeric matrices through graft polymerization offers various advantages by providing new properties, allowing for additional chemical reactions that the matrix alone could not undergo or that would require drastic chemical conditions to occur. In this work, epoxy groups were incorporated through a graft polymer of poly(glycidyl methacrylate), using a prefunctionalization with peroxide groups in the polytetrafluoroethylene matrix through gamma radiation. These peroxide groups were subsequently used as radical chemical initiators in the graft polymerization reaction of glycidyl methacrylate. The graft polymerization reaction was studied based on the absorbed dose, monomer concentration, reaction time, and temperature. [ABSTRACT FROM AUTHOR]

Radiation-induced graft polymerization of poly(N-vinylcaprolactam) onto silicone catheters by direct irradiation method was studied. The effects of the irradiation dose, as well as the monomer concentration, on the grafting efficiency were studied. The conditions for achieving maximum grafting yield were observed at 30% of monomer concentration in toluene at 50 kGy. The graft polymerization was examined by different characterization methods, including measurements such as thermogravimetric analysis, infrared, water contact angle, and swelling. The temperature-responsive behavior of smart grafted copolymer was studied by swelling at different temperatures. Differently from pristine silicone catheter, the N-vinylcaprolactam-grafted catheters were able to load vancomycin and sustain the release for 30 h. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop a drug delivery copolymer. Hydroxyethyl methacrylate (HEMA) was grafted onto poly(tetrafluoroethylene) films using gamma rays as the initiator agent. The optimal conditions for the grafting procedure were determined through a series of experiments, considering the following factors: reaction time, temperature, HEMA concentration, solvent type, and gamma-ray doses. Grafting was accomplished using the oxidative-pre-irradiation method. The resulting copolymer was subjected to various characterizations, including thermal analysis (TGA and DSC), FTIR-ATR spectroscopy, contact angle measurements, and assessment of physicochemical properties. Additionally, its ability to load and release ciprofloxacin was evaluated. [ABSTRACT FROM AUTHOR]

The grafting of stimuli-responsive polymers into medical devices to create functional materials has attracted the attention of scientific community. The capacity of these polymers to change its conformation reversibly as function of variables of the environment in which it is applied, is well taken into account to create drug delivery systems. Because cotton gauzes are materials of priority use in biomedical area, and they are susceptible to develop biofilm on its surface contaminating skin wounds. This work proposes the modification of cotton gauze with a dual stimuli-responsive copolymer, composed of two monomers such as methacrylic acid and N-isopropylacrylamide, through a grafting copolymerization induced by chemical initiator and gamma radiation. Experimental conditions were evaluated for each method. Grafting was verified by infrared spectroscopy (FTIR-ATR) and scanning electron microscopy as well as its thermal behavior was determined through thermogravimetric analysis. Critical pH was confirmed by potentiometric titrations finding a value of 4.7 for grafted cotton gauzes and their critical temperature ranging between 31 and 34 °C, which was determined by water uptake as function of temperature. The loading and release of norfloxacin were tested, finding that grafted gauzes exhibited affinity for this drug and it is released under simulated physiological conditions of temperature and pH. Norfloxacin-loaded gauzes show their efficiency inhibiting Escherichia coli and Staphylococcus aureus growth in a contaminated environment, at different pH values. This improvement of cotton gauzes can serve as barrier to avoid the formation of biofilm in surgical conditions and for wound healing. [ABSTRACT FROM AUTHOR]

Polymeric medical devices have become essential for healthcare because of their advantageous characteristics; however, by themselves, these polymers cannot stop pathogenic contamination. Since this is an important unresolved issue, this work proposes the study of the loading and release of ciprofloxacin, a broad-spectrum antibiotic onto polyacrylic acid/polyethylene glycol dimethacrylate (AAc/EGDMA) modified PDMS films. Effective loading and release of the antibiotic was studied by UV–Vis experiments verifying kinetics following the Peppas–Sahlin model of release for ciprofloxacin. Additionally, the films were tested in cell growth inhibition tests and cytotoxicity assays in which they showed effective inhibition of E. coli while also maintaining good cytocompatibility. [ABSTRACT FROM AUTHOR]

Poly(N-vinylimidazole) and its quaternized counterpart were successfully grafted onto cotton gauzes by performing radical polymerization reactions of N-vinylimidazole using high energy γ-radiation derived from a 60Co radioactive as a clean initiator method. The obtained materials were then characterized by FTIR, DSC, TGA, and SEM to confirm the presence of the functional polymer in the gauzes. Additionally, pH titrations were performed to the solid substrates to evaluate their acid–base properties confirming that the modified gauzes behave as a polyelectrolyte buffer acid–base system with a pKa ≈ 5.6. Furthermore, to evaluate the applicability of the gauzes, elongation tests (ASTM-D5035) were performed to the pristine and the modified gauzes to evaluate their mechanical performance, finding that the mechanical properties of the gauzes were not significantly changed after the modification procedure. Finally, bacterial growth inhibition and hemolysis tests were performed to assess the antimicrobial performance of the gauzes and their biocompatibility, having found that these medical devices are effective in inhibiting the growth of S. aureus while proving non-hemolytic to human erythrocytes. [ABSTRACT FROM AUTHOR]

Non-conventional uranium extraction sources are not the most used mainly due to high extraction costs associated with low concentrations and chemical forms that require extra purification processes. Therefore, efforts should focus on cheaper processes and develop more effective extraction materials. In this investigation, ionic-imprinted polymers were synthesized for the selective extraction of uranyl ions in aqueous solution, using polyesters of 2,5-bis((allyloxy)carbonyl)terephthalic acid and 4,6-bis((allyloxy)carbonyl)isophthalic acid as base materials and polymerized by gamma radiation. The extraction capacity (Q) of the resins was evaluated by varying parameters such as pH, temperature, extraction time, and ionic strength. [ABSTRACT FROM AUTHOR]

Cotton gauze fabric was functionalized with 2-(dimethylamino)ethyl methacrylate (DMAEMA) with the aim of developing wound dressings with antibiofilm activity and tunable debriding activity. Cotton-g-DMAEMA gauzes were prepared via one-step grafting (direct method) using Co γ-rays as source to initiate the polymerization process. The effects of absorbed dose, dose rate, and monomer concentration on the degree of grafting were evaluated in detail. Some cotton-g-DMAEMA gauzes were subsequently quaternized with methyl iodide. Grafting of DMAEMA and sequential quaternization were confirmed by FTIR-ATR spectroscopy; thermal properties were analyzed using TGA, and morphology by scanning electron microscopy. Grafting of DMAEMA gauzes enhanced blood absorption and collagenase activity, while further quaternization led to a remarkable inhibition of the proteinase activity. Their antimicrobial features were analyzed by evaluating their biofilm inhibiting and biofilm eradicating properties in an in vitro chronic wound model. Although the non-quaternized gauzes only displayed moderate biofilm inhibitory properties at best, the quaternized cotton-g-DMAEMA bearing the highest content of DMAEMA displayed strong biofilm inhibiting and biofilm eradicating properties. This indicates that quaternized cotton-g-DMAEMA gauzes are less prone to be colonized by bacteria and can notably reduce the number of colonies in an infected wound. [ABSTRACT FROM AUTHOR]

The aim of this work was to functionalize cotton gauzes with cyclodextrins in order to endow them with the ability to elute antimicrobial agents and to prevent infections. Gauzes were modified according to a two-steps approach: (1) pre-irradiation of the gauzes (Gammabeam) to graft glycidyl methacrylate (GMA), and (2) covalent binding of cyclodextrins (CDs) to the GMA-grafted gauzes. First the dependence of GMA grafting yield on the radiation dose (from 1 to 20 kGy) and the time of reaction was evaluated in detail. Anchorage of β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) was confirmed by FTIR, TGA, and 3-methylbenzoic acid sorption. Differently from pristine gauzes, CD-functionalized GMA-grafted gauzes were able to load an anionic antibiotic drug, specifically nalidixic acid, and to sustain the release for 6 h. Drug-loaded gauzes were tested in vitro against E. coli and the results prove the suitability of the functionalization approach to efficiently inhibit the growth of this microorganism. [ABSTRACT FROM AUTHOR]

Both poly[2-(dimethylamino) ethyl methacrylate] (PDMAEMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) were radiation grafted onto polypropylene films (PP) using gamma radiation from a 60Co source. PP was pre-irradiated by gamma ray for modification following by grafted PDMAEMA and PEGMEMA by a one step method. Grafting was studied as a function of the pre-irradiation dose between 20 and 180 kGy, dose rate of 10.4 kGy/h, and monomer concentration 50% of PDMAEMA/PEGMEMA (1/1) in different solvents (toluene, acetone, and methanol). FTIR-ATR, TGA, and DSC were carried out in the characterization of the graft copolymer obtained. Stimuli-responsive behavior and critical pH point were studied by swelling in water. pH and thermo-responsive films of PE-g-(DMAEMA/PEGMEMA) presented a lower critical solution temperature (LCST) of 50 °C and critical pH point around 8.7. [ABSTRACT FROM AUTHOR]

Radiation-induced graft polymerization of acryloyl chloride onto films of polyolefins (polyethylene and polypropylene) using gamma radiation was investigated in order to establish a convenient method to obtain polymer films grafted with polyacrylic esters. Grafting was carried out by three different methods; (i) direct irradiation of film in monomer solution (ii) vapor phase irradiation method, and (iii) pre-irradiation in air. The effects of monomer concentration, radiation dose and methods of grafting, on the formation of grafted polyolefins are reported in this paper. [ABSTRACT FROM AUTHOR]

In order to study the nature of interaction of arylbutadiynes with transient free radicals, polymerization and copolymerization of some vinyl monomers such as methyl methacrylate (MMA), styrene (ST), methacrylonitrile (MAN), vinylidene chloride (VCl2), ethyl acrylate (EA) and acrylonitrile (AN), were carried out in the presence of diphenylbutadiyne (DPB), 4,4'-butadiynylene-N,N,N',N'-tetra- n-butyl-dibenzamide (BBA), and 4,4'-dibromodiphenylbutadiyne (BPB). MMA gave an intense ESR signal at the polymerization temperature when the polymerization system became viscous, and the number of radicals increased with polymerization time. Strong signals of polyEA and polyMAN radicals were also observed in the presence of DPB when the polymerization system became almost solid. This is a unique case where active transient propagating radicals such as that of polyEA can be detected at polymerization temperature. The rates of polymerization decreased by the presence of the diacetylenes, but the molecular weights did not change with the diacetylene concentrations. UV spectroscopy revealed that there was no diacetylene unit bonded to the obtained polymers, indicating that degradative chain transfer is not the case. The monomer reactivity ratios for MMA-ST and MMA-AN systems did not vary significantly in the presence of the diacetylenes, although some difference was observed. It seems that some arylbutadiynes interact with free radicals but do not form bonds. [ABSTRACT FROM AUTHOR]

Radiation-induced graft polymerization of N,N-dimethylaminoethyl-metacrylate onto low density polyethylene (LDPE) film by the preirradiation method in presence of air was investigated. The appropriate reaction conditions at which the graft polymerization was carried out are reported. [ABSTRACT FROM AUTHOR]

The gamma-ray induced, solid state crosslinking of polynorbornene(PolyNB) and its copolymer was studied. PolyNB degradates when irradiated in air, but it is readily crosslinked in vacuum. Homopolymer and copolymers containing a stabilizing group, 3,5-di- tert-butyl-4-hydroxybenzoyloxy group, were resistant to crosslinking showing induction periods before crosslinking. The irradiated PolyNB showed an ESR signal due to the allyl radical, and the polymer containing the hydroxybenzoyloxy group showed a signal due to the quinolic radical. [ABSTRACT FROM AUTHOR]

Free radical copolymerization of 4-phenylbut-1-en-3-yne (PB) with methyl methacrylate(MMA) was studied. The polymerization of MMA was inhibited by the presence of small amounts of PB, but the copolymerization yield increased with increase in the PB concentration, and PB-rich copolymers were obtained. The monomer reactivity ratios, r and r, were found to be 0.096 and 2.83, respectively. The Q and e values of PB were calculated by using the values of MMA and were found to be 2.69 and 0.74, respectively. The slow polymerization and low molecular weights were attributed to the low propagating activity of PB radicals. [ABSTRACT FROM AUTHOR]