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The study examines the experiences of patients with skin diseases such as acne, psoriasis or atopic eczema in their relationships with their treating doctors. Evidence indicates the need to educate general practitioners on the psychological effects of skin diseases and to educate them and dermatologists on the means to diagnose and manage, or appropriately refer, the conditions.

Objectives:This study explored the suitability and benefits of problem-based learning (PBL) in competency-based postgraduate public health training. The PBL was delivered within a rural retreat and included site visits. Methods:Qualitative semistructured interviews with trainee public health officers and key informants. Results:The learning approach (retreat–PBL combination with site visits) was valuable and relevant. Trainees reported a high learning impact with increased knowledge about the problems examined and rural public health practice. They also expressed an openness to work rurally. Conclusion:Collaboratively developed and delivered, experiential rural public health PBL provides a positive learning experience for trainees undertaking competency-based training in public health and could play an important workforce role. PBL appears to be suitable in rural and non-rural public health training settings.

Vinyl chloride monomer (VCM) has been employed as a chain transfer agent to yield polyolefins with one vinyl end group per chain; subsequent incorporation of these macromonomers has resulted in the formation of branched polyolefins. The use of VCM as a comonomer in transition-metal-catalyzed olefin polymerizations results in β-chloride elimination, yielding polymers that contain vinyl end groups and a chlorinated catalyst. Through reactivation of the catalyst by advantageous MAO, or other aluminum alkyl, reinitiation of the olefin polymerization can occur; the combination of elimination and reactivation allows for VCM to behave as a chain transfer agent. The use of VCM as a chain transfer agent results in the exclusive formation of vinyl end groups (no vinylidene or internal vinyl end groups) in polyethylenes, both homopolyethylene and copolymers with octene; in propylene polymerizations, vinyl end groups are formed in addition to vinylidene end groups, the result of β-hydride elimination which occurs even in the absence of VCM. The chain transfer constants for VCM in ethylene polymerizations for a variety of single site catalysts were determined and found to be very similar, with Cs × 10⁴ ~ 30; for a propylene polymerization using a zirconocene catalyst, Cs × 10⁴ ~ 700. It was further observed that the resulting macromonomers formed in the polyethylene polymerizations could be incorporated into the growing polymer chains, resulting in the formation of long chain branches.

The optimization of the synthesis of homopolymers from n-butyl acrylate (BA), styrene (Sty), and methyl methacrylate (MMA), using copper-based atom transfer radical polymerization (ATRP) with tris(2-dimethylaminoethyl)amine (Me6-TREN) as a ligand is reported. Catalyst concentration (copper bromide complexed with 1 equiv of Me6-TREN) as low as 1% relative to initiator (50 ppm in the reaction mixture) was sufficient to successfully prepare well-defined poly(n-butyl acrylate) in bulk. With 50% catalyst to initiator, styrene was polymerized in bulk. The deactivator species had poor solubility in nonpolar solvents. Finally, the polymerization of methyl methacrylate with CuBr/Me6-TREN required the use of a high concentration of catalyst and the addition of Cu(II)Cl2 at the beginning of the reaction; the resulting polymers were of higher molecular weight than predicted by theory and had relatively broad molecular weight distributions.

Reverse atom transfer radical polymerization (ATRP) of n-butyl methacrylate was conducted in an aqueous dispersed system. Using a water-soluble initiator (V-50), a nonionic surfactant (Brij 98), and a hydrophobic ligand (dNbpy) to complex a copper halide, polymers with relatively well controlled molar masses and low polydispersities were obtained. Stable latexes with particle diameters within 150−300 nm were formed. Kinetic studies were performed under various experimental conditions. The influence of the concentrations of the catalyst, the surfactant, and the initiator as well as the temperature on the polymerization rate, molecular weight, and particle size was investigated. Because of the lack of high molecular weight polymer during the early polymerization stage, reverse ATRP in the aqueous dispersed system presumably has a different “nucleation” mechanism from that of a conventional emulsion polymerization. In addition, fast decomposition of the initiator prevents the continuous entry of radicals into the particles from the aqueous phase. As a result, the kinetics of the reverse ATRP is fundamentally different from a classical emulsion polymerization and is controlled mainly by the atom transfer equilibrium.

Halide anions have been used as complexing ligands in iron-mediated ATRP, in both direct and reverse ATRP. In direct ATRP, iron(II) bromide complexed with ammonium and phosphonium chloride, bromide, or iodide salts has been shown to catalyze the polymerization of both styrene and (meth)acrylates in a controlled manner under appropriate conditions. The experimental molecular weights increased linearly with monomer conversion and were close to the calculated values. The polymerization rates and polydispersities (Mw/Mn = 1.1−1.4) were dependent on the monomer employed. Reverse ATRP, initiated by AIBN/FeBr3/onium salts, led to a controlled polymerization of both methyl methacrylate and methyl acrylate, while for styrene uncontrolled molecular weights and high polydispersities were obtained, presumably due to the involvement of the cationic polymerization. It is suggested that different iron complexes may be involved in ATRP, depending on the onium salt/FeBr3 ratio. Because of their ionic nature, the iron complexes could be removed easily from the reaction mixture by washing the polymerization mixture with water.

The controlled/“living” radical polymerization of n-butyl methacrylate was conducted in an emulsion under reverse atom transfer radical polymerization (ATRP) conditions. The initiators used were conventional water-soluble initiators, such as potassium persulfate (KPS), 2,2‘-azobis(2-methylpropionamidine) dihydrochloride (V-50), and 2,2‘-azobis[2-(2-dimidazolin-2-yl)propane] dihydrochloride (VA-044). The transition metal catalyst employed was copper(II) dibromide with 4,4‘-dialkyl-2,2‘-bipyridine as the ligands.

Atom transfer radical polymerization (ATRP) has been used to directly prepare linear pHEMA of controlled molecular weight and low polydispersity. Reaction conditions were adjusted to successfully polymerize the functional, polar methacrylate monomer. These adjustments included the use of a mixed solvent system consisting of methyl ethyl ketone and 1-propanol, lowering the temperature to 50 °C or less and using an alkyl bromide initiator with a copper chloride catalyst. The Cu/2,2‘-bipyridyl (bpy) complex, normally a heterogeneous mixture in nonpolar, organic solvents, was completely soluble in the above solvent system. A block copolymer was prepared with a poly(methyl methacrylate) macroinitiator. The monomer can also be protected and polymerized under conditions very similar to those used for the ATRP of methyl methacrylate.

Atom transfer radical polymerization (ATRP) has been successfully carried out in supercritical carbon dioxide (scCO2) for the polymerization of fluorinated (meth)acrylates. In particular, well-controlled polymerizations have been obtained with the use of a fluoroalkyl-substituted 2,2‘-bipyridine ligand. Block copolymers comprised of fluorinated (meth)acrylates and poly(MMA) (MMA = methyl methacrylate) or poly(DMAEMA) (DMAEMA = 2-(dimethylamino)ethyl methacrylate) were produced in scCO2 by ATRP. In addition, the dispersion polymerization of MMA using ATRP in scCO2 in the presence of a fluorinated polymeric surfactant stabilizer was successfully carried out to yield poly(MMA) latex particles with controlled molecular weight and a narrow molecular weight distribution.

The controlled/“living” radical polymerization of n-butyl acrylate (n-BA) and 2-trimethylsilyloxyethyl acrylate (TMS−HEA) by atom transfer radical polymerization (ATRP) is reported. Di- and triblock copolymers with predefined block lengths and low polydispersities were obtained, using methyl 2-bromopropionate as the initiator, Cu^IBr as catalyst and N,N,N‘,N‘‘,N‘‘-pentamethyldiethylenetriamine as the ligand. Hydrolysis of the trimethylsilyl groups led to block copolymers with n-BA and 2-hydroxyethyl acrylate (HEA) units which were characterized by SEC, ¹H NMR, and DSC. Diblock copolymers of n-BA and HEA could also be obtained by successive addition of the two monomers, in that order. The amphiphilic di- and triblock copolymers formed dispersions in water.

The homopolymerization of 2-((2-bromopropionyl)oxy)ethyl acrylate (BPEA) by atom transfer radical polymerization (ATRP), a “living”/controlled radical polymerization system, has yielded a hyperbranched polymer. Variation of the reaction conditions and especially the concentration of copper(II) in the polymerization system affects not only the rate of polymerization but also the chain architecture. The copper(II) concentration in the polymerization medium is affected by solvent, the ligand used to complex copper, and temperature. The effects of temperature and ligand on the polymerization rate and the resulting chain architecture were studied.

The self-condensing vinyl polymerization (SCVP) of 2-((2-bromopropionyl)oxy)ethyl acrylate (BPEA) has resulted in the formation of hyperbranched polyacrylates. The polymerization mechanism used to polymerize the BPEA was atom transfer radical polymerization (ATRP), a “living”/controlled radical polymerization. This paper details the study of the kinetics of polymerization and the growth of the macromolecule during the polymerization. The results obtained in the polymerization were compared to the theoretical predictions for SCVP. It was determined that the polymerization deviated from the ideal case, as a consequence of the establishment of a dynamic equilibrium in ATRP resulting in the addition of more than one monomer unit in a single activation step.