Lennart Piculell

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A model for simulating the drug release from a swelling and dissolving polymer tablet is presented and verified to data. The model is based on a mechanistic approach, and it can therefore be employed to study the sensitivity of true physical constants, for instance the drug diffusion coefficient or the drug solubility. The model generates the drug and(More)
The aim of the study was to determine and compare the degree of swelling and the swelling kinetics of poly(ethylene oxide) (PEO) hydrophilic matrix tablets without any additives for matrixes with different molecular weight polydispersities. A wide range of "mixed" polydisperse PEO tablets were obtained by mixing two PEO batches with average molecular(More)
The aim of this work was to study intermolecular interactions in systems containing charged polyion (polyacrylate, PA(-)), charged surfactant (C(16)TA(+)) and nonionic surfactant (C(12)E(5) or C(12)E(8)). To achieve this we have created four different phase diagrams using two different so-called complex salts, C(16)TAPA(25) and C(16)TAPA(6000), both(More)
Mixtures of the added salts NaI and CsI can be used to gradually 'tune' the propensity of kappa-carrageenan (KC) helices to aggregate in solution. We show that this method can be used to resolve the molecular events by which helix formation, under certain conditions, leads to gelation. We also present an overview of the various states of aggregation and(More)
Cryo-transmission electron microscopy (cryo-TEM), viscometry and optical rotation have been used to study the microstructure of dilute solutions of helical kappa-carrageenan under varied electrolyte composition (0.1 M of NaI, CsI and mixtures of the two salts). Microfibers (300-400 nm in length) were observed above a critical cesium content, while below(More)
Complexes of oppositely charged polymers and surfactants (OCPS) in water come in many varieties, including liquid-crystalline materials, soluble complexes, structured nanoparticles, and water-insoluble surface layers. The range of available structures and properties increases even further with the addition of other amphiphilic substances that may enter, or(More)
Mixtures of locust bean gum (LBG) with kappa-carrageenan (KC) in 0.1 M aqueous solutions of the mixed salts NaI/CsI were investigated by cryo-transmission electron microscopy (cryo-TEM) and dynamic viscoelastic measurements. Previous studies have shown that as the cesium content is increased in such mixed salt solutions, a transition occurs from molecularly(More)
The redissolution of water-insoluble polyion-surfactant ion complexes by added excess of surfactant has systematically been investigated in experimental and theoretical phase equilibrium studies. A number of stoichiometric polyion-surfactant ion "complex salts" were synthesized and they consisted of akyltrimethylammonium surfactant ions of two different(More)
This review summarizes recent progress in our understanding of aquoeus "complex salts" of ionic surfactants with polymeric counterions. Complex salts are simplified versions of the much-studied mixtures of oppositely charged polyelectrolytes and surfactants, and are also good model systems to study the fundamentals of polyion-mediated forces in colloidal(More)
The influence of added colloidal particles on the phase separation of mixed aqueous polymer solutions is investigated. Two types of particles (polystyrene latex or silica) and different combinations of segregating polymers (dextran of varying molar mass combined with poly(ethylene oxide) (PEO) of varying molar mass, or Ucon, a copolymer of ethylene oxide(More)