| 1. |
- Andersson, Mats R., et al.
(author)
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Regioselective polymerization of 3-(4-octylphenyl)thiophene with FeCl3
- 1994
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In: Macromolecules. - : American Chemical Society. - 0024-9297 .- 1520-5835. ; 27:22, s. 6503-6506
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Journal article (peer-reviewed)abstract
- We have shown that it is possible to regioselectively polymerize 3-(4-octylphenyl) thiophene with FeCl3. Adding FeCl3 slowly to the monomer leads to a soft and therefore regioselective polymerization. The head-to-tail content was determined by H-1 NMR to be 94 +/- 2%. Thin films of the polymer treated with chloroform vapor have an absorption maximum at 602 nm (2.06 eV) with clear vibronic fine structure. Free standing films have a conductivity of 4 S/cm, which is 100 times higher than for earlier prepared poly(3-(4-octylphenyl)thiophene). A mechanism for the regioregular polymerization is also proposed.
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| 2. |
- Björling, Mikael
(author)
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Interaction between Surfaces with Attached Poly(ethylene oxide) Chains
- 1992
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In: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 25:15, s. 3956-3970
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Journal article (peer-reviewed)abstract
- The paper presents a self-consistent mean-field lattice theory of the Scheutjens-Fleer type where segments may adapt to temperature and the local environment by changing their distribution among internal states. Some new features are introduced in the theoretical treatment of incompressible systems, and it is demonstrated how the chemical potential may be calculated without reference to a bulk system. The theory is applied to make a qualitative prediction for the interaction between surfaces with grafted poly-(ethylene oxide), or PEO, chains. A simple two-state model for the PEO segments is used. The attractive force between the PEO-covered surfaces in water is predicted to be related to the temperature-dependent solubility of PEO in water. The contributions to the force are illustrated by simple examples. The attractive force does not change monotonically upon changing the graft density. At low coverages a strong bridging attraction is predicted if the surfaces are hydrophobic. As the surfaces become more polar, repulsion sets in at a larger separation and the overall attraction becomes less strong. A calculated, closed, solubility gap for a crude model of micelles of nonionic surfactants is presented.
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| 3. |
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| 4. |
- Johansson, Hans-Olof, et al.
(author)
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Experimental and Theoretical Study of Phase Separation in Aqueous Solutions of Clouding Polymers and Carboxylic Acids
- 1993
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In: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 26:17, s. 4478-4483
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Journal article (peer-reviewed)abstract
- The phase behavior of different carboxylic acids/nonionic polymer/water systems has been studied. The carboxylic acids investigated are acetic acid, propionic acid, and butyric acid. The polymers used are a linear random copolymer of ethylene oxide and propylene oxide (UCON) and ethyl(hydroxyethyl)-cellulose (EHEC). These polymers display a lower critical solution temperature (LCST) in water. The decrease of the polarity in the carboxylic acids as the carbon chain increases causes a decrease of the LCST of the system carboxylic acid/polymer/water. As a consequence of this the two-phase region expands. The experimentally determined phase diagrams can qualitatively be described and compared with a theoretical model, based on Flory-Huggins theory of polymer solubility. The cloud-point temperature of the systems decreases as the difference between the effective interaction of polymer-cosolute and cosolute-water increases.
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| 5. |
- Linse, Per, et al.
(author)
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Lattice Theory for Multicomponent Mixtures of Copolymers with Internal Degrees of Freedom in Heterogeneous Systems
- 1991
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In: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 24:25, s. 6700-6711
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Journal article (peer-reviewed)abstract
- We have generalized the lattice theory recently presented by Evers, Scheutjens, and Fleer (Macromolecules 1990, 23, 5221) by extending it to the case where the polymer segments possess internal degrees of freedom. The theory is able to describe the adsorption from a multicomponent mixture of arbitrary composition of polymers and solvents where the segments of a polymer may be of different types and possess internal degrees of freedom. The use of internal states results in effective segment-segment interaction parameters, which are temperature and density dependent. This simple polymer model has previously been useful for describing the existence of a lower consolute point occurring in some aqueous polymer solutions and for predicting the conformational equilibrium of poly(ethylene oxide) in homogeneous solutions. We also present results from an application of our extended theory on the adsorption of Pluronic (a triblock copolymer) from aqueous solution. The nontrivial and prominent increase of the Pluronic adsorption as the temperature of the solution reaches the cloud point from below is accurately reproduced by the theory.
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| 6. |
- Torstensson, Maria, et al.
(author)
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Monomeric surfactants for surface modification of polymers
- 1990
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In: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 23:1, s. 126-132
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Journal article (peer-reviewed)abstract
- The surfaces of poly(methy1 methacrylate) and a UV-curable acrylic lacquer have been modified by the addition of small amounts of polymerizable, monomeric surfactants and a surface-active polymer. In the system used, the surfactants concentrate at interfaces toward less polar phases. Addition of 1% w/w of a monomeric surfactant to an acrylic lacquer gives a surface concentration of 50% at the interface toward air. The rate of surface enrichment is primarily dependent on the size of the surfactant molecules and on the viscosity of the bulk material to which it is added. Comparison shows that the surfactant-modified surface layers are thicker than monolayers made by the Langmuir-Blodgett technique. The behavior of monomeric surfactants in the outmost surface layer of a modified film is, however, similar to that of a monolayer formed in a Langmuir-Blodgett balance. Contact angle hysteresis measurements show that the surface-active monomers concentrating in the surface of a modified lacquer film become more and more closely packed when the total surfactant concentration is increased.
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