Displaying publications 1 - 20 of 100 in total

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  1. Electro polymerized 4-vinyl pyridine on 2B pencil graphite as ionophore for cadmium (II)
    Wee Ling JL, Khan A, Saad B, Ab Ghani S
    Talanta, 2012 Jan 15;88:477-83.
    PMID: 22265529 DOI: 10.1016/j.talanta.2011.11.018
    A new poly(4-vinyl pyridine) (P4VP) based cadmium (Cd)-ion selective electrode (ISE) was developed. The 4-vinyl pyridine (4VP) was first polymerized electrochemically on the surface of graphite, later characterized by FTIR, SEM/EDX and then optimized as ISE for Cd. At optimal pH 6.4, slope of 27.7±0.8mVdecade(-1), linear concentration range of 1×10(-7) to 1.0×10(-1)M Cd(2+) and limit of detection (S/N=3) of 2.51×10(-8)M were obtained. The ISE was very selective towards Cd(2+), with K(pot)<1×10(-2) in the presence of the usual cations and anions in water samples. Response time and shelf life of less than 1min and 90 days, respectively, were observed. Its application was tested in various types of samples.
    Matched MeSH terms: Polymerization
  2. Ultrasonic assisted ultrafiltration process for emulsification of oil field produced water treatment
    Agi A, Junin R, Alqatta AYM, Gbadamosi A, Yahya A, Abbas A
    Ultrason Sonochem, 2019 Mar;51:214-222.
    PMID: 30401623 DOI: 10.1016/j.ultsonch.2018.10.023
    Ultrafiltration has been proven to be very effective in the treatment of oil-in-water emulsions, since no chemical additives are required. However, ultrafiltration has its limitations, the main limits are concentration polarization resulting to permeate flux decline with time. Adsorption, accumulation of oil and particles on the membrane surface which causes fouling of the membrane. Studies have shown that the ultrasonic is effective in cleaning of fouled membrane and enhancing membrane filtration performance. But the effectiveness also, depends on the selection of appropriate membrane material, membrane geometry, ultrasonic module design, operational and processing condition. In this study, a hollow and flat-sheet polyurethane (PU) membranes synthesized with different additives and solvent were used and their performance evaluated with oil-in-water emulsion. The steady-state permeate flux and the rejection of oil in percentage (%) at two different modes were determined. A dry/wet spinning technique was used to fabricate the flat-sheet and hollow fibre membrane (HFMs) using Polyethersulfone (PES) polymer base, Polyvinylpyrrolidone (PVP) additive and N, N-Dimethylacetamide (DMAc) solvent. Ultrasonic assisted cross-flow ultrafiltration module was built to avoid loss of ultrasonic to the surrounding. The polyurethane (PU) was synthesized by polymerization and sulphonation to have an anionic group (-OH; -COOH; and -SO3H) on the membrane surface. Changes in morphological properties of the membrane had a significant effect on the permeate flow rate and oil removal. Generation of cavitation and Brownian motion by the ultrasonic were the dominant mechanisms responsible for ultrafiltration by cracking the cake layers and reducing concentration polarization at the membrane surface. The percentage of oil after ultrafiltration process with ultrasonic is about 90% compared to 49% without ultrasonic. Ultrasonic is effective in enhancing the membrane permeate flux and controlling membrane fouling.
    Matched MeSH terms: Polymerization
  3. Controlled release studies through chitosan-based hydrogel synthesized at different polymerization stages
    Md Rasib SZ, Md Akil H, Khan A, Abdul Hamid ZA
    Int J Biol Macromol, 2019 May 01;128:531-536.
    PMID: 30708001 DOI: 10.1016/j.ijbiomac.2019.01.190
    An earlier study showed that the behaviour of chitosan-poly(methacrylic acid‑co‑N‑isopropylacrylamide) [chitosan‑p(MAA‑co‑NIPAM)] hydrogels synthesized at different reaction times are affected with regard to their pH and temperature sensitivities. The study was continued in this paper to identify the effects of different reaction times on the degradation, efficiency of rifampicin (Rif) loading and the Rif release profile under two different pH conditions (acidic and basic). The results that were obtained showed that the hydrogel had a faster degradation rate in the acidic condition than in the basic condition, where there was a loss of approximately 50% and 20%, respectively in its original weight within two weeks. The Rif loading efficiency was within 50% and the drug release was controlled by characteristics that were developed beyond the polymerization stages of the synthesis. Therefore, the reaction time for the synthesis of the hydrogel can be considered as a way to control the behaviour of the hydrogel as well as to modify the drug release profile in the chitosan‑p(MAA‑co‑NIPAM) hydrogel.
    Matched MeSH terms: Polymerization*
  4. Fulltext Synthesis and evaluation of a molecularly imprinted polymer for 2,4-dinitrophenol
    Zakaria ND, Yusof NA, Haron J, Abdullah AH
    Int J Mol Sci, 2009 Jan;10(1):354-65.
    PMID: 19333450 DOI: 10.3390/ijms10010354
    Molecular imprinted polymers (MIP) are considered one of the most promising selective and novel separation methods for removal phenolic compound in wastewater treatment. MIP are crosslinked polymeric materials that exhibit high binding capacity and selectivity towards a target molecule (template), purposely present during the synthesis process. In this work MIP were prepared in a bulk polymerization method in acetonitrile using 2,4-dinitrophenol, acrylamide, ethylene glycol dimethacrylate, and benzoyl peroxide as template, functional monomer, cross-linker and initiator, respectively. An adsorption process for removal of nitrophenol using the fabricated MIP was evaluated under various pH and time conditions. The parameters studied for 2,4-dinitrophenol includes adsorption kinetics, adsorption isotherm, and selectivity. The maximum adsorption of nitrophenol by the fabricated MIP was 3.50 mg/g. The adsorption of 2,4-dinitrophenol by the fabricated MIP was found effective at pH 6.0. A kinetics study showed that nitrophenol adsorption follows a second order adsorption rate and the adsorption isotherm data is explained well by the Langmuir model.
    Matched MeSH terms: Polymerization
  5. Application of polymethylmethacrylate-grafted cellulose as reinforcement for compatibilised polylactic acid/natural rubber blends
    Rosli NA, Ahmad I, Anuar FH, Abdullah I
    Carbohydr Polym, 2019 Jun 01;213:50-58.
    PMID: 30879689 DOI: 10.1016/j.carbpol.2019.02.074
    In this study, modified agave cellulose fibre combined by graft copolymerisation with methylmethacrylate was tested as a potential reinforcement for polylactic acid (PLA)-natural rubber/liquid natural rubber blends. Mechanical, morphological, thermal, wetting, and biodegradation characterisations were performed to assess the influence of cellulose-graft-polymethylmethacrylate (cell-g-PMMA) content on the properties of biocomposites. The addition of cell-g-PMMA improved the mechanical properties of the composites because of the chemical interaction between PLA and PMMA. Thermal stability decreased slightly upon cell-g-PMMA addition because of the low thermal stability of PMMA. A soil burial test revealed that the degradation of composites decreased with an increase in the cell-g-PMMA content. However, the weight loss after burial, which directly affected the water absorption capacity, was still higher for the cell-g-PMMA composites than for the polymer alone.
    Matched MeSH terms: Polymerization
  6. Fulltext Synthesis and Thermal Properties of Acrylonitrile/Butyl Acrylate/Fumaronitrile and Acrylonitrile/Ethyl Hexyl Acrylate/Fumaronitrile Terpolymers as a Potential Precursor for Carbon Fiber
    Jamil SNAM, Daik R, Ahmad I
    Materials (Basel), 2014 Sep 01;7(9):6207-6223.
    PMID: 28788187 DOI: 10.3390/ma7096207
    A synthesis of acrylonitrile (AN)/butyl acrylate (BA)/fumaronitrile (FN) and AN/EHA (ethyl hexyl acrylate)/FN terpolymers was carried out by redox polymerization using sodium bisulfite (SBS) and potassium persulphate (KPS) as initiator at 40 °C. The effect of comonomers, BA and EHA and termonomer, FN on the glass transition temperature (Tg) and stabilization temperature was studied using Differential Scanning Calorimetry (DSC). The degradation behavior and char yield were obtained by Thermogravimetric Analysis. The conversions of AN, comonomers (BA and EHA) and FN were 55%-71%, 85%-91% and 76%-79%, respectively. It was found that with the same comonomer feed (10%), the Tg of AN/EHA copolymer was lower at 63 °C compared to AN/BA copolymer (70 °C). AN/EHA/FN terpolymer also exhibited a lower Tg at 63 °C when compared to that of the AN/BA/FN terpolymer (67 °C). By incorporating BA and EHA into a PAN system, the char yield was reduced to ~38.0% compared to that of AN (~47.7%). It was found that FN reduced the initial cyclization temperature of AN/BA/FN and AN/EHA/FN terpolymers to 228 and 221 °C, respectively, in comparison to that of AN/BA and AN/EHA copolymers (~260 °C). In addition, FN reduced the heat liberation per unit time during the stabilization process that consequently reduced the emission of volatile group during this process. As a result, the char yields of AN/BA/FN and AN/EHA/FN terpolymers are higher at ~45.1% and ~43.9%, respectively, as compared to those of AN/BA copolymer (37.1%) and AN/EHA copolymer (38.0%).
    Matched MeSH terms: Polymerization
  7. Fulltext Fly ash porous material using geopolymerization process for high temperature exposure
    Abdullah MM, Jamaludin L, Hussin K, Bnhussain M, Ghazali CM, Ahmad MI
    Int J Mol Sci, 2012;13(4):4388-95.
    PMID: 22605984 DOI: 10.3390/ijms13044388
    This paper presents the results of a study on the effect of temperature on geopolymers manufactured using pozzolanic materials (fly ash). In this paper, we report on our investigation of the performance of porous geopolymers made with fly ash after exposure to temperatures from 600 °C up to 1000 °C. The research methodology consisted of pozzolanic materials (fly ash) synthesized with a mixture of sodium hydroxide and sodium silicate solution as an alkaline activator. Foaming agent solution was added to geopolymer paste. The geopolymer paste samples were cured at 60 °C for one day and the geopolymers samples were sintered from 600 °C to 1000 °C to evaluate strength loss due to thermal damage. We also studied their phase formation and microstructure. The heated geopolymers samples were tested by compressive strength after three days. The results showed that the porous geopolymers exhibited strength increases after temperature exposure.
    Matched MeSH terms: Polymerization
  8. Fulltext DNA Adsorption Studies of Poly(4,4'-Cychlohexylidene Bisphenol Oxalate)/Silica Nanocomposites
    Al Balawi AN, Yusof NA, Kamaruzaman S, Mohammad F, Wasoh H, Al-Lohedan HA
    Materials (Basel), 2019 Apr 11;12(7).
    PMID: 30978916 DOI: 10.3390/ma12071178
    The present study deals with the synthesis, characterization, and DNA extraction of poly(4,4'-cyclohexylidene bisphenol oxalate)/silica (Si) nanocomposites (NCs). The effects of varying the monomer/Si (3.7%, 7%, and 13%) ratio towards the size and morphology of the resulting NC and its DNA extraction capabilities have also been studied. For the NC synthesis, two different methods were followed, including the direct mixing of poly(4,4'-cyclohexylidene bisphenol oxalate) with fumed Si, and in situ polymerization of the 4,4'-cyclohexylidene bisphenol monomer in the presence of fumed silica (11 nm). The formed NCs were thoroughly investigated by using different techniques such as scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), powdered X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) analysis where the results supported that there was the successful formation of poly(4,4'-cyclohexylidene bisphenol oxalate)/Si NC. Within the three different NC samples, the one with 13% Si was found to maintain a very high surface area of 12.237 m²/g, as compared to the other two samples consisting of 7% Si (3.362 m²/g) and 3.7% Si (1.788 m²/g). Further, the solid phase DNA extraction studies indicated that the efficiency is strongly influenced by the amount of polymer (0.2 g > 0.1 g > 0.02 g) and the type of binding buffer. Among the three binding buffers tested, the guanidine hydrochloride/EtOH buffer produced the most satisfactory results in terms of yield (1,348,000 ng) and extraction efficiency (3370 ng/mL) as compared to the other two buffers of NaCl (2 M) and phosphate buffered silane. Based on our results, it can be indicated that the developed poly(4,4'-cyclohexylidene bisphenol oxalate)/Si NC can serve as one of the suitable candidates for the extraction of DNA in high amounts as compared to other traditional solid phase approaches.
    Matched MeSH terms: Polymerization
  9. Fulltext The Effect of Filler Content And Storage Conditions on Linear Dimensional Change and Accuracy of the Experimental Prisma Ap.HComposite Inlay Material
    Razak, A.A.A., Harrison, A., Alani, A.A.
    Ann Dent, 1996;3(1):-.
    MyJurnal
    The effect of filler content and storage conditions such as drying, storing in water and thermal cycling on linear dimensional changes were investigated and evaluated. The dimensional accuracy studies were performed using a specific designed mould and a coordinate measuring machine. The findings gave support to the view that tiller content is an important factor influencing the physical and mechanical properties of the composite inlay material. The higher tiller content gave less polymerization shrinkage. The greatest linear shrinkage recorded was 0.79 %. The average linear shrinkage (in air, water and thermal cycling) for 79 % filler Prisma AP.H was 0.33 %, for 65 % tiller Prisma AP.H was 0.35 % and for 50 % filler Prisma AP.H was 0.42 %. Generally, dimensional changes was greatest when stored dry. This was followed by materials which were thermal cycled. The least dimensional change recorded was when the materials were stored in water.
    Matched MeSH terms: Polymerization
  10. Fulltext Production and purification of polymerization-competent HIV-1 capsid protein p24 (CA) in NiCo21(DE3) Escherichia coli
    Teow SY, Mualif SA, Omar TC, Wei CY, Yusoff NM, Ali SA
    BMC Biotechnol, 2013;13:107.
    PMID: 24304876 DOI: 10.1186/1472-6750-13-107
    HIV genome is packaged and organized in a conical capsid, which is made up of ~1,500 copies of the viral capsid protein p24 (CA). Being a primary structural component and due to its critical roles in both late and early stages of the HIV replication cycle, CA has attracted increased interest as a drug discovery target in recent years. Drug discovery studies require large amounts of highly pure and biologically active protein. It is therefore desirable to establish a simple and reproducible process for efficient production of HIV-1 CA.
    Matched MeSH terms: Polymerization
  11. Optimization and modelling of enzymatic polymerization of ε-caprolactone to polycaprolactone using Candida Antartica Lipase B with response surface methodology and artificial neural network
    Pakalapati H, Tariq MA, Arumugasamy SK
    Enzyme Microb Technol, 2019 Mar;122:7-18.
    PMID: 30638510 DOI: 10.1016/j.enzmictec.2018.12.001
    Recently enzymatic catalysts have replaced organic and organometallic catalysts in the synthesis of bio-resorbable polymers. Enzymatic polymerization is considered as an alternative to conventional polymerization as they are less toxic, environmental friendly and can operate under mild conditions. In this research, the enzymatic ring-opening polymerization (e-ROP) of e-caprolactone (e-CL) using Candida Antartica Lipase B (CALB) as catalyst to produce the Polycaprolactone. Two modelling techniques namely response surface methodology (RSM) and artificial neural network (ANN) have been used in this work. RSM is used to optimize the parameters and to develop a model of the process. ANN is used to develop the model to predict the results obtained from the experiment. The parameters involved are time, reaction temperature, mixing speed and enzyme-solvent ratio. The experimental result is Polydispersity index (PDI) of the polymer. The experimental data obtained was adequately fitted into second-order polynomial models. Simulation was done using artificial neural network model developed with Mean absolute error (MAD) value of 1.65 in comparison with MAD value of 7.4 for RSM. The Regression value (R2) values of RSM and ANN were found to be 0.96 and 0.93 respectively. The predictive models were validated experimentally and were found to be in agreement with the experimental values.
    Matched MeSH terms: Polymerization
  12. Fulltext Novel, one-step synthesis of zwitterionic polymer nanoparticles via distillation-precipitation polymerization and its application for dye removal membrane
    Ibrahim GPS, Isloor AM, Inamuddin, Asiri AM, Ismail N, Ismail AF, et al.
    Sci Rep, 2017 Nov 21;7(1):15889.
    PMID: 29162869 DOI: 10.1038/s41598-017-16131-9
    In this work, poly(MBAAm-co-SBMA) zwitterionic polymer nanoparticles were synthesized in one-step via distillation-precipitation polymerization (DPP) and were characterized. [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA) as monomer and N, N'-methylene bis(acrylamide) (MBAAm) as cross-linker are used for the synthesis of nanoparticles. As  far as our knowledge, this is the first such report on the synthesis of poly(MBAAm-co-SBMA) nanoparticles via DPP. The newly synthesized nanoparticles were further employed for the surface modification of polysulfone (PSF) hollow fiber membranes for dye removal. The modified hollow fiber membrane exhibited the improved permeability (56 L/ m2 h bar) and dye removal (>98% of Reactive Black 5 and >80.7% of Reactive orange 16) with the high permeation of salts. Therefore, the as-prepared membrane can have potential application in textile and industrial wastewater treatment.
    Matched MeSH terms: Polymerization
  13. Studies on the effects of titanate and silane coupling agents on the performance of poly (methyl methacrylate)/barium titanate denture base nanocomposites
    Elshereksi NW, Ghazali MJ, Muchtar A, Azhari CH
    J Dent, 2017 Jan;56:121-132.
    PMID: 27916635 DOI: 10.1016/j.jdent.2016.11.012
    OBJECTIVES: This study aimed to fabricate and characterise silanated and titanated nanobarium titanate (NBT) filled poly(methyl methacrylate) (PMMA) denture base composites and to evaluate the behaviour of a titanate coupling agent (TCA) as an alternative coupling agent to silane. The effect of filler surface modification on fracture toughness was also studied.

    METHODS: Silanated, titanated and pure NBT at 5% were incorporated in PMMA matrix. Neat PMMA matrix served as a control. NBT was sonicated in MMA prior to mixing with the PMMA. Curing was carried out using a water bath at 75°C for 1.5h and then at 100°C for 30min. NBT was characterised via Fourier transform-infrared spectroscopy (FTIR), Transmission Electron Microscopy (TEM) and Brunauer-Emmett-Teller (BET) analysis before and after surface modification. The porosity and fracture toughness of the PMMA nanocomposites (n=6, for each formulation and test) were also evaluated.

    RESULTS: NBT was successfully functionalised by the coupling agents. The TCA exhibited the lowest percentage of porosity (0.09%), whereas silane revealed 0.53% porosity. Statistically significant differences in fracture toughness were observed among the fracture toughness values of the tested samples (p<0.05). While the fracture toughness of untreated samples was reduced by 8%, an enhancement of 25% was achieved after titanation. In addition, the fracture toughness of the titanated samples was higher than the silanated ones by 10%.

    CONCLUSION: Formation of a monolayer on the surface of TCA enhanced the NBT dispersion, however agglomeration of silanated NBT was observed due to insufficient coverage of NBT surface. Such behaviour led to reducing the porosity level and improving fracture toughness of titanated NBT/PMMA composites. Thus, TCA seemed to be more effective than silane.

    CLINICAL SIGNIFICANCE: Minimising the porosity level could have the potential to reduce fungus growth on denture base resin to be hygienically accepTable Such enhancements obtained with Ti-NBT could lead to promotion of the composites' longevity.

    Matched MeSH terms: Polymerization
  14. Smart pH-responsive co-polymeric hydrogels for controlled delivery of capecitabine: Fabrication, Optimization and in vivo toxicology screening
    Rehman U, Sarfraz RM, Mahmood A, Hussain Z, Thu HE, Zafar N, et al.
    Curr Drug Deliv, 2021 Feb 11.
    PMID: 33583374 DOI: 10.2174/1567201818666210212085912
    BACKGROUND: Despite exhibiting promising anticancer potential, the clinical significance of capecitabine (a potent prodrug of 5-fluorouracil used for treatment of colorectal cancer) is limited owing to its acidic and enzymatic hydrolysis, lower absorption following the oral administration, poor bioavailability, short plasma half-life and poor patient compliance.

    OBJECTIVES: The present study was aimed to fabricate the capecitabine as smart pH-responsive hydrogel network to efficiently facilitate its oral delivery while shielding its stability in the gastric media.

    METHODS: The smart pH sensitive HP-β-CD/agarose-g-poly(MAA) hydrogel network was developed using an aqueous free radical polymerization technique. The developed hydrogels were characterized for drug-loading efficiency, structural and compositional features, thermal stability, swelling behaviour, morphology, physical form, and release kinetics. The pH-responsive behaviour of developed hydrogels was established by conducting the swelling and release behaviour at different pH values (1.2 and 7.4), demonstrating significantly higher swelling and release at pH 7.4 as compared with pH 1.2. The capecitabine-loaded hydrogels were also screened for acute oral toxicity in animals by analysing the body weight, water and food intake, dermal toxicity, ocular toxicity, biochemical analysis, and histological examination.

    RESULTS: The characteristic evaluations revealed that capecitabine (anticancer agent) was successfully loaded into the hydrogel network. Capecitabine loading was ranged from 71.22% to 90.12%. An interesting feature of hydrogel was its pH-responsive behaviour which triggers release at basic pH (94.25%). Optimum swelling (95%) was seen at pH 7.4. Based upon regression coefficient R2 (0.96 - 0.99) best fit model was zero order. The extensive toxicity evaluations evidenced good safety profile with no signs of oral, dermal or ocular toxicities, as well as no variations in blood parameters and histology of vital organs.

    CONCLUSION: Our findings conclusively evinced that the developed hydrogel exhibited excellent pharmaceutical and therapeutic potential and thus can be employed as pH-responsive system for controlled delivery of anticancer agents.

    Matched MeSH terms: Polymerization
  15. Synthesis of α,β-Unsaturated Carbonyl-Based Compounds, Oxime and Oxime Ether Analogs as Potential Anticancer Agents for Overcoming Cancer Multidrug Resistance by Modulation of Efflux Pumps in Tumor Cells
    Qin HL, Leng J, Zhang CP, Jantan I, Amjad MW, Sher M, et al.
    J Med Chem, 2016 Apr 14;59(7):3549-61.
    PMID: 27010345 DOI: 10.1021/acs.jmedchem.6b00276
    Sixty-nine novel α,β-unsaturated carbonyl based compounds, including cyclohexanone, tetralone, oxime, and oxime ether analogs, were synthesized. The antiproliferative activity determined by using seven different human cancer cell lines provided a structure-activity relationship. Compound 8ag exhibited high antiproliferative activity against Panc-1, PaCa-2, A-549, and PC-3 cell lines, with IC50 value of 0.02 μM, comparable to the positive control Erlotinib. The ten most active antiproliferative compounds were assessed for mechanistic effects on BRAF(V600E), EGFR TK kinases, and tubulin polymerization, and were investigated in vitro to reverse efflux-mediated resistance developed by cancer cells. Compound 8af exhibited the most potent BRAF(V600E) inhibitory activity with an IC50 value of 0.9 μM. Oxime analog 7o displayed the most potent EGFR TK inhibitory activity with an IC50 of 0.07 μM, which was analogous to the positive control. Some analogs including 7f, 8af, and 8ag showed a dual role as anticancer and MDR reversal agents.
    Matched MeSH terms: Polymerization
  16. Fulltext Radiation-induced formation of acrylated palm oil nanoparticle using pluronic f-127 microemulsion system
    Tajau, R., Wan Yunus, W.M.Z., Mohd Dahlan, K.Z., Mahmood, M.H., Hashim, K., Ismail, M., et al.
    Pertanika Journal of Science & Technology, 2013;21(1):127-134.
    MyJurnal
    This study demonstrated the utilization of radiation-induced initiator methods for the formation of
    nanoparticles of Acrylated Palm Oil (APO) using aqueous Pluronic F-127 (PF-127) microemulsion
    system. This microemulsion system was subjected to gamma irradiation to form the crosslinked APO
    nanoparticles. Dynamic light scattering (DLS), Fourier Transform Infrared (FTIR) spectroscopy and
    Transmission Electron Microscopy (TEM) were used to characterize the size and the chemical structure
    of the nanoparticles. As a result, the size of the APO nanoparticle was decreased when the irradiation
    dose increased. The decrease in size might be due to the effects of intermolecular crosslinking and
    intramolecular crosslinking reactions of the APO nanoparticles during irradiation process. The size of the
    nanoparticle is in the range of 98 to 200 nanometer (nm) after irradiation using gamma irradiator. This radiation-induced method provides a free initiator
    induced and easy to control process as compared
    to the classical or chemical initiator process. The
    study has shown that radiation-induced initiator
    methods, namely, polymerization and crosslinking
    in the microemulsion, were promising for the
    synthesis of nanoparticles.
    Matched MeSH terms: Polymerization
  17. Lipase catalyzed ultrasonic synthesis of poly-4-hydroxybutyrate-co-6-hydroxyhexanoate
    Gumel AM, Annuar MS, Chisti Y
    Ultrason Sonochem, 2013 May;20(3):937-47.
    PMID: 23231942 DOI: 10.1016/j.ultsonch.2012.09.015
    Four different lipases were compared for ultrasound-mediated synthesis of the biodegradable copolymer poly-4-hydroxybutyrate-co-6-hydroxyhexanoate. The copolymerization was carried out in chloroform. Of the enzymes tested, Novozym 435 exhibited the highest copolymerization rate, in fact the reaction rate was observed to increase with about 26-fold from 30 to 50°C (7.9×10(-3)Ms(-1)), sonic power intensity of 2.6×10(3)Wm(-2) and dissipated energy of 130.4Jml(-1). Copolymerization rates with the Candida antarctica lipase A, Candida rugosa lipase, and Lecitase Ultra™ were lower at 2.4×10(-4), 1.3×10(-4) and 3.5×10(-4)Ms(-1), respectively. The catalytic efficiency depended on the enzyme. The efficiency ranged from 4.15×10(-3)s(-1)M(-1) for Novozym 435-1.48×10(-3)s(-1)M(-1) for C. rugosa lipase. Depending on the enzyme and sonication intensity, the monomer conversion ranged from 8.2% to 48.5%. The sonication power, time and temperature were found to affect the rate of copolymerization. Increasing sonication power intensity from 1.9×10(3) to 4.5×10(3)Wm(-2) resulted in an increased in acoustic pressure (P(a)) from 3.7×10(8) to 5.7×10(8)Nm(-2) almost 2.4-3.7 times greater than the acoustic pressure (1.5×10(8)Nm(-2)) that is required to cause cavitation in water. A corresponding acoustic particle acceleration (a) of 9.6×10(3)-1.5×10(4)ms(-2) was calculated i.e. approximately 984-1500 times greater than under the action of gravity.
    Matched MeSH terms: Polymerization
  18. Fulltext The flexural strengths of five commercially available tooth-coloured restorative materials
    Sulaiman, E., Yeo, Y.M., Chong, Y.T.
    Ann Dent, 2007;14(1):39-45.
    MyJurnal
    Purpose of the study: The objective of this study was to investigate the flexural strengths of five commercially available tooth-coloured restorative materials – Alpha-Dent (composite resin, Dental Technologies Inc.), Solare Anterior (composite resin, GC), F2000 (polyacid-modified composite resin, 3M), Beautifil (giomer, Shofu) and Fuji II LC (resin- modified glass ionomer cement, GC] using the ISO 4049 specifications. Materials and Method: Ten specimens of (25±0.2)mm x (2±0.1)mm x (2±0.1)mm from each material were prepared at 22-23ºC using a customized metal mould. After light polymerization, the specimens were stored in distilled water at 37ºC for 24 hours. The specimens were subsequently blotted dry, measured and subjected to flexural testing using an Instron Universal Testing Machine with a crosshead speed of 0.5mm/min. The flexural strengths were calculated from the maximum load exerted on the specimens. Data were analysed using one way ANOVA and scheffe’s post-hoc multiple comparison tests at a significance level of 0.05.Results: The results showed that the mean flexural strengths of Beautifil, Solare Anterior and Alpha-Dent were above 80 MPa and those of F2000 and Fuji II LC were below 80 MPa. The results of one-way ANOVA and Scheffe’s post-host tests demonstrated that Beautifil had significantly higher mean flexural strength compared to Fuji II LC, F2000 and Alpha-Dent (P
    Matched MeSH terms: Polymerization
  19. Fulltext Membraneless polyester microdroplets as primordial compartments at the origins of life
    Jia TZ, Chandru K, Hongo Y, Afrin R, Usui T, Myojo K, et al.
    Proc Natl Acad Sci U S A, 2019 08 06;116(32):15830-15835.
    PMID: 31332006 DOI: 10.1073/pnas.1902336116
    Compartmentalization was likely essential for primitive chemical systems during the emergence of life, both for preventing leakage of important components, i.e., genetic materials, and for enhancing chemical reactions. Although life as we know it uses lipid bilayer-based compartments, the diversity of prebiotic chemistry may have enabled primitive living systems to start from other types of boundary systems. Here, we demonstrate membraneless compartmentalization based on prebiotically available organic compounds, α-hydroxy acids (αHAs), which are generally coproduced along with α-amino acids in prebiotic settings. Facile polymerization of αHAs provides a model pathway for the assembly of combinatorially diverse primitive compartments on early Earth. We characterized membraneless microdroplets generated from homo- and heteropolyesters synthesized from drying solutions of αHAs endowed with various side chains. These compartments can preferentially and differentially segregate and compartmentalize fluorescent dyes and fluorescently tagged RNA, providing readily available compartments that could have facilitated chemical evolution by protecting, exchanging, and encapsulating primitive components. Protein function within and RNA function in the presence of certain droplets is also preserved, suggesting the potential relevance of such droplets to various origins of life models. As a lipid amphiphile can also assemble around certain droplets, this further shows the droplets' potential compatibility with and scaffolding ability for nascent biomolecular systems that could have coexisted in complex chemical systems. These model compartments could have been more accessible in a "messy" prebiotic environment, enabling the localization of a variety of protometabolic and replication processes that could be subjected to further chemical evolution before the advent of the Last Universal Common Ancestor.
    Matched MeSH terms: Polymerization
  20. Fulltext Electrical conductivity of anionic surfactant-doped polypyrrole nanoparticles prepared via emulsion polymerization
    Ghalib, H., Abdullah, I., Daik, R.
    Pertanika Journal of Science & Technology, 2013;21(2):459-472.
    MyJurnal
    Conducting polypyrrole (PPy) nanoparticles were synthesized by chemical oxidative polymerization of pyrrole in aqueous solution containing ferric sulfate (Fe2(SO4)3), anionic surfactants (sodium dodecylbenzene-sulfonate (NaDBS) or sodium dodecyl sulfate (SDS)), 1-pentanol as the oxidant, dopant and co-emulsifier, respectively. The polymerization was carried out at 0 ºC and 25 ºC. Fourier transform infrared spectroscopy (FTIR) and elemental analysis indicated that anionic surfactants were successfully incorporated into the PPy backbone. Incorporation of anionic surfactants caused enhanced electrical conductivity, increased yield, decreased the size of particles as well as improved the thermal stability of the resultant PPy. The presence of anionic surfactant seems to inhibit undesirable side reactions so as to improve the regularity of the PPy backbone. Globular PPy particles were obtained with diameter ranged from 40 to 118 nm as revealed by field emission scanning electron microscopy (FE-SEM) and conductivity of 7.89×10-4 –2.35×10-2 S cm-1, as measured using impedance analyzer. It was found that polymerization at low temperature (0 ºC) produced PPy particles with smaller size and higher conductivity. The sodium dodecyl sulfate-doped PPy (SDS-doped PPy) exhibited higher conductivity than that of the sodium dodecylbenzenesulfonate-doped PPy (NaDBS-doped PPy), due to the bulkiness of NaDBS as compared to SDS.
    Matched MeSH terms: Polymerization
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