Recent developments in miniemulsion polymerization

Some developments in miniemulsion polymerization aiming at taking advantage of its unique mechanisms minimizing the drawbacks of this technique are discussed. The discussion ineludes preparation of highly concentrated latexes, miniemulsion polymerization in continuous stirred tank reactors (CSTRs), and elimination of the low molecular weight hydrophobe

Evaluation of pH-sensitive poly(2-hydroxyethyl methacrylate-co-2-(diisopropylamino)ethyl methacrylate) copolymers as drug delivery systems for potential applications in ophthalmic therapies/ocular delivery of drugs

Smart polymers like pH sensitive systems can improve different pharmacological treatment. In this work the behavior of copolymers containing 2-hydroxyethyl methacrylate (HEMA) with different proportions of 2-(diisopropylamino) ethyl methacrylate (DPA) and different amounts of cross-linker agent, ethylene glycol dimethacrylate (EGDMA) are evaluated as pH-sensitive drug delivery systems for potential application in ophthalmic therapies. A detailed characterization of the pH-responsive behavior was performed by swelling studies and scanning electron microscopy (SEM) analysis. Drug loading and release studies at different pH values were evaluated using Rhodamine 6G (Rh6G) as a model drug. The interaction between Rh6G and hydrogels was studied by Fourier Transform Infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The results show that the presence of DPA in the copolymers confers pH-responsive properties to the polymer, as noted in swelling and SEM studies, when the pH decreases below 7.40 the swelling degree increases and a porous morphology is observed. The apparent pKa of copolymers was estimated between 6.80 and 7.17 depending on the composition. The amount of Rh6G loaded depends mainly on the medium pH and the interaction between the drug and the copolymers, observed by SEM and FTIR spectrum. The release of Rh6G of copolymers p(HEMA/DPA) show a normal Fickian or anomalous diffusion behavior at different pH values, depending on the HEMA/DPA ratio

Surface, thermal, and mechanical properties of composites and nanocomposites of polyurethane/PTFE nanoparticles

Sem informaçãoFilms from blends of polyurethane and nano-polytetrafluoroethylene aqueous dispersions (PU/nanoPTFE) were prepared, and the effect of the addition of different amounts of PTFE nanoparticles (50 nm) was studied. The changes in the superficial properties of the films were studied by means of XPS, ATR/FTIR, and contact angle measurements. SEM and TEM results are also included. The contact angle values confirm the surface hydrophobicity of composite films. Even though nanoparticles are present in the bulk, higher concentrations of particles appear at the surface in samples with lower nanoPTFE content (up to 10 wt%), as revealed by XPS. Higher amounts of nanoPTFE particles cause aggregation. The mechanical and thermal properties of composites are also discussed. © 2014 Springer Science+Business Media.Films from blends of polyurethane and nano-polytetrafluoroethylene aqueous dispersions (PU/nanoPTFE) were prepared, and the effect of the addition of different amounts of PTFE nanoparticles (50 nm) was studied. The changes in the superficial properties of the films were studied by means of XPS, ATR/FTIR, and contact angle measurements. SEM and TEM results are also included. The contact angle values confirm the surface hydrophobicity of composite films. Even though nanoparticles are present in the bulk, higher concentrations of particles appear at the surface in samples with lower nanoPTFE content (up to 10 wt%), as revealed by XPS. Higher amounts of nanoPTFE particles cause aggregation. The mechanical and thermal properties of composites are also discussed.Films from blends of polyurethane and nano-polytetrafluoroethylene aqueous dispersions (PU/nanoPTFE) were prepared, and the effect of the addition of different amounts of PTFE nanoparticles (50 nm) was studied. The changes in the superficial properties of the films were studied by means of XPS, ATR/FTIR, and contact angle measurements. SEM and TEM results are also included. The contact angle values confirm the surface hydrophobicity of composite films. Even though nanoparticles are present in the bulk, higher concentrations of particles appear at the surface in samples with lower nanoPTFE content (up to 10 wt%), as revealed by XPS. Higher amounts of nanoPTFE particles cause aggregation. The mechanical and thermal properties of composites are also discussed.168111Sem informaçãoSem informaçãoSem informaçãoAbdulkadir, A., Baki, H., Yusuf, M., Sefix, S., Synthesis, characterization and surface properties of amphiphilic polystyrene-b-polypropylene glycol block copolymers (2006) Eur Polym J, 42, pp. 740-750Balkenende, A.R., Van De, B.H.J.A.P., Scholten, M., Willard, N.P., Evaluation of different approaches to assess the surface tension of low-energy solids by means of contact angle measurements (1998) Langmuir, 14 (20), pp. 5907-5912Beamson, G., Briggs, D., (1992) High Resolution XPS of Organic Polymers - The Scienta ESCA300 Database, , John Wiley & Sons, New YorkChattopadhyay, D.K., Mishra, A.K., Sreedhar, B., Raju, K.V.S.N., Thermal and viscoelastic properties of polyurethane-imide/clay hybrid coatings (2006) Polym Degrad Stab, 91, pp. 1837-1849Durrieu, V., Gandini, A., Belgacem, M.N., Blayo, A., Eisele, G., Putaux, J.-L., Preparation of aqueous anionic poly-(urethane-urea) dispersions: Influence of the nature and proportion of the urethane groups on the dispersion and polymer properties (2004) Journal of Applied Polymer Science, 94 (2), pp. 700-710. , DOI 10.1002/app.20933Eckesley, S.T., Helmer, B.J., Mechanistic considerations of particle size effects on film properties of hard/soft latex blends (1997) J Coat Technol, 69, pp. 97-107Giani, E., Sparnacci, K., Laus, M., Palamone, G., Kapeliouchko, V., Arcella, V., TFE - polystyrene core - shell nanospheres and nanocomposites (2003) Macromolecules, 36, pp. 4360-4367Hosokawa, M., Nogi, K., Naito, M., Yokoyama, T., (2007) Nanoparticle Technology Handbook, p. 18. , Elsevier, AmsterdamHuang, T., Lu, R., Wang, H., Ma, Y., Tian, J., Li, T., Investigation on the tribological properties of POM modified by nano-PTFE (2011) J Macromol Sci B Phys, 50, pp. 1235-1248Jeong, H.Y., Lee, M.H., Kim, B.K., Surface modification of waterborne polyurethane (2006) Colloids and Surfaces A: Physicochemical and Engineering Aspects, 290 (1-3), pp. 178-185. , DOI 10.1016/j.colsurfa.2006.05.036, PII S0927775706004146Kapeliouchko, V., Palamone, G., Poggio, T., Zuccheri, G., Passeri, R., Sparnacci, K., Antonioli, D., Laus, M., PMMA-based core-shell nanoparticles with various PTFE cores (2009) J Polym Sci a, 47, pp. 2928-2937Król, P., Synthesis methods, chemical structures and phase structures of linear polyurethanes (2007) Prog Mat Sci, 52, pp. 915-1015Lai, Y.K., Lin, C.J., Wang, H., Huang, H.Y., Zhuang, H.F., Superhydrophilic-superhydrophobic micropattern on TiO2 nanotube films by photocatalytic lithography (2008) Electrochem Commun, 10, pp. 387-391Lakshmi, R.V., Basu, B.J., Fabrication of superhydrophobic sol-gel composite films using hydrophobically modified colloidal zinc hydroxide (2009) J Colloid Interface Sci, 339, pp. 454-460Lee, M.H., Jang, M.K., Kim, B.K., Surface modification of high heat resistant UV cured polyurethane dispersions (2007) European Polymer Journal, 43 (10), pp. 4271-4278. , DOI 10.1016/j.eurpolymj.2007.07.044, PII S0014305707004491Li, M., Zhai, J., Liu, H., Song, Y.L., Jiang, L., Zhu, D.B., Electrochemical deposition of conductive superhydrophobic zinc oxide thin films (2003) J Phys Chem B, 107, pp. 9954-9957Liu, H., Shang, Q., Xiao, G., Lv, J., Fabrication of stable superhydrophobic coatings with bicomponent polyurethane/polytetrafluoroethylene composites (2011) Asian J Chem, 23, pp. 2866-2870Marchese, E., Kapeliouchko, V., Colaiana, P., TFE polymerization process (2001), US Patent 6,297,334Meng, H.F., Wang, S.T., Xi, J.M., Tang, Z.Y., Jiang, L., Facile means of preparing super amphiphobic surfaces on common engineering metals (2008) J Phys Chem C, 112, pp. 11454-11458Owens, D.K., Wendt, R.C., Estimation of the surface free energy of polymers (1969) J Appl Polym Sci, 13, pp. 1741-1747Pan, L.N., Dong, H.R., Bi, P.Y., Chemical preparation of aluminum superhydrophobic surface with nano-micro mixed structure by SDBS/HCl etching method (2009) J Chin Univ-Chin, 30, pp. 1371-1374Pardini, O.R., Amalvy, J.I., FTIR, 1H-NMR spectra, and thermal characterization of water-based polyurethane/acrylic hybrids (2008) Journal of Applied Polymer Science, 107 (2), pp. 1207-1214. , DOI 10.1002/app.27188Peruzzo, P.J., Anbinder, P.S., Pardini, O.R., Costa, C.A., Leite, C.A., Galembeck, F., Amalvy, J.I., Polyurethane/acrylate hybrids: Effects of the acrylic content and thermal treatment on the polymer properties (2010) J Appl Polym Sci, 116, pp. 2694-2705Pompe, G., Haussler, L., Adam, G., Eichhorn, K.-J., Janke, A., Hupfer, B., Lehmann, D., Reactive polytetrafluoroethylene/polyamide 6 compounds. 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Study of the reactivity with respect to the functionality of the polytetrafluoroethylene component and analysis of the notched impact strength of the polytetrafluoroethylene/polyamide 6 compounds (2005) Journal of Applied Polymer Science, 98 (3), pp. 1317-1324. , DOI 10.1002/app.22274Righetti, M.C., Boggioni, A., Laus, M., Antonioli, D., Sparnacci, K., Boarino, L., Thermal and mechanical properties of PES/PTFE composites and nano composites (2013) J Appl Polym Sci, 55, pp. 3624-3633Righetti, M.C., Boggioni, A., Laus, M., Antonioli, D., Sparnacci, K., Enrico, E., Boarino, L., Ageing reduction in PES through the incorporation of rigid non-interacting PTFE nano particles (2013) Thermochim Acta, 571, pp. 53-59Sparnacci, K., Antonioli, D., Deregibus, S., Laus, M., Poggio, T., Kapeliouchko, V., Palamone, G., PTFE-based core-soft shell nanospheres and soft matrix nanocomposites (2009) Macromolecules, 42, pp. 3518-3524Yamauchi, G., Riko, Y., Yasuno, Y., Shimizu, T., Funakoshi, N., Water-repellent coating for mobile phone microphones (2005) Surface Coatings International Part B: Coatings Transactions, 88 (4), pp. 281-283. , http://docserver.ingentaconnect.com/deliver/cw/occa/14764865/v88n4/s9/ p281.pdf?fmt=dirpdf&tt=9295&cl=25&ini=connect&bini=&wis= connect&ac=0&acs=32629,75000325&expires=1136452051&checksum= 6CDF8AF717B23CC81A0D602F5A7E9D01&cookie=1111044864Yiang, C.Y., Krimm, S., Infrared spectra of high polymers. III. Polytetrafluoroethylene and polychlorotrifluoroethylene (1956) J Chem Phys, 25, pp. 563-571Zheng, Z.R., Gu, Z.Y., Huo, R.T., Ye, Y.H., Superhydrophobicity of polyvinylidene fluoride membrane fabricated by chemical vapor deposition from solution (2009) Appl Surf Sci, 255, pp. 7263-7267Zhu, M., Zuo, W., Yu, H., Yang, W., Chen, Y., Superhydrophobic surface directly created by electrospinning based on hydrophilic material (2006) Journal of Materials Science, 41 (12), pp. 3793-3797. , DOI 10.1007/s10853-005-5910-zWe thank CICPBA, ANPCyT (PICT 2011–0238), and CONICET for their financial assistance, L. F. Gambino and O.R. Pardini for technical assistance, Christopher Young for reviewing and correcting the paper and Solvay Specialty Polymers S.p.A. (Italy) for the donation of the nanoPTFE dispersion. PSA and PJP are the members of CONICET and JIA is the member of CICPBA (Argentina)

Film-forming microgels for pH-triggered capture and release

The pH-responsive behavior for a series of lightly cross-linked, sterically stabilized poly(tertiary amine methacrylate) - based latexes adsorbed onto mica and silica was investigated using in situ tapping mode AFM at room temperature. The adsorbed layer structure was primarily determined by the glass transition temperature, Tg of the latex: poly[2-(diethylamino)ethyl methacrylate] - based particles coalesced to form relatively featureless uniform thin films, whereas the higher Tg poly[2-(diisopropylamino)ethyl methacrylate] latexes retained their original particulate character. Adsorption was enhanced by using a cationic poly[2-(dimethylamino)ethyl methacrylate] steric stabilizer, rather than a nonionic poly(ethylene glycol)-based stabilizer, since the former led to stronger electrostatic binding to the oppositely charged substrate. Both types of adsorbed latexes acquired cationic microgel character and swelled appreciably at low pH, even those that had coalesced to form films. Fluorescence spectroscopy was used to study the capture of a model hydrophobic probe, pyrene, by these adsorbed latex layers followed by its subsequent release by lowering the solution pH. The repeated capture and release of pyrene through several pH cycles was also demonstrated. Since these poly(tertiary amine methacrylate) latexes are readily prepared by aqueous emulsion polymerization and adsorption occurs spontaneously from aqueous solution, this may constitute an attractive route for the surface modification of silica, mica and other oxides

Síntesis y caracterización de un sistema electroestimulado

Los hidrogeles electroconductores son compuestos 3D formados por matrices poliméricas de distinta naturaleza como los  hidrogeles y los polímeros conductores, los cuales le confieren al compósito propiedades ópticas, eléctricas y redox únicas. Estos materiales híbridos  pueden ser utilizados como biomateriales   en biosensoresimplantables o sistemas de suministro controlado de medicamentos.  En el presente trabajo se estudió la síntesis y caracterización de un sistema electroestimulado a partir de polipirrol (PPy) y el microgel responsivo a base de poli(2-dietilamino etilimetacrilato) (pDEAEMA). Además se investigó la liberación electroestimulada usando Rodamina 6G (Rh6G) como droga modelo