Experimental determination of the temperature–concentration diagram of flexible polymer solutions by neutron scattering

Cotton, J. P.; Nierlich, Martine; Boué, François; Daoud, M.; Farnoux, B.; Jannink, G.; Duplessix, R.; Picot, C.

doi:10.1063/1.433172

Cited by 183 publications

(113 citation statements)

References 16 publications

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“…According to simulation findings (Foteinopoulou et al, 2008;Laso and Karayiannis, 2008;Laso et al, 2009), four distinct scaling regimes can be clearly ascertained, in accordance to theoretical predictions (Fleer et al, 1993) (Chaikin and Lubensky, 2000). corresponding crossover thresholds have been proposed to be <p*' seml (N) ~N~0 764 (Cotton et al, 1976), q>*-mi^ ~ <p MR J/2 and q>*-conc ~ 0.59, the latter two being proposed through graph theoretical proof . The predicted values for the threshold con- 1993; Laso and Karayiannis, 2008).…”

Section: Characteristic Scaling Regimessupporting

confidence: 51%

Monte Carlo simulations of densely-packed athermal polymers in the bulk and under confinement

Foteinopoulou

Karayiannis

Laso

2015

Chemical Engineering Science

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HIGHLIGHTS• Identification of the maximally random jammed state for polymer packings.• Molecular simulation of the phase transition in hard-sphere chains.• Molecular modelling of the effect of confinement in densely-packed athermal polymers.• Numerical calculation of the topological constraints in polymeric systems.• First-principles calculation of the scaling regimes in flexible polymers. ABSTRACTWe review the main results from extensive Monte Carlo (MC) simulations on athermal polymer packings in the bulk and under confinement. By employing the simplest possible model of excluded volume, macromolecules are represented as freely-jointed chains of hard spheres of uniform size. Simulations are carried out in a wide concentration range: from very dilute up to very high volume fractions, reaching the maximally random jammed (MRJ) state. We study how factors like chain length, volume fraction and flexibility of bond lengths affect the structure, shape and size of polymers, their packing efficiency and their phase behaviour (disorder-order transition). In addition, we observe how these properties are affected by confinement realized by fiat, impenetrable walls in one dimension. Finally, by mapping the parent polymer chains to primitive paths through direct geometrical algorithms, we analyse the characteristics of the entanglement network as a function of packing density.

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Section: Characteristic Scaling Regimessupporting

confidence: 51%

Monte Carlo simulations of densely-packed athermal polymers in the bulk and under confinement

Foteinopoulou

Karayiannis

Laso

2015

Chemical Engineering Science

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“…The PLLA/CH 2 Cl 2 solution with doubled concentration was spin-coated on a glass substrate to produce films with thickness larger than 1 μm so that film thickness effect can be eliminated [31]. Both concentrations for solvent casting and spin coating solutions are lower than the overlap concentration c , which is between 0.6 and 2.3 g/ml as calculated by [32] M…”

Section: Materials and Methods Sample Preparation And Annealingmentioning

confidence: 99%

Effect of Film Formation Method and Annealing on Crystallinity of Poly(L-Lactic Acid) Films

Hsu

Yao

2011

ASME 2011 International Manufacturing Science and Engineering Conference, Volume 1

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Poly(L-lactic acid) (PLLA) has been shown to have potential medical usage such as in drug delivery because it can degrade into bioabsorbable products in physiological environments, and its degradation is affected by crystallinity. In this paper, the effect of film formation method and annealing on the crystallinity of PLLA are investigated. The films are made through solvent casting and spin coating methods, and subsequent annealing is conducted. The resulting crystalline morphology, structure, conformation, and intermolecular interaction are examined using optical microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. It is observed that solvent casting produces category 1 spherulites while annealed spin coated films leads to spherulites of category 2. Distinct lamellar structures and intermolecular interactions in the two kinds of films have been shown. The results enable better understanding of the crystallinity in PLLA, which is essential for its drug delivery application. INTRODUCTIONThere is a significant interest in use of biodegradable polymers due to their biocompatibility and biodegradability. Poly lactic acid (PLA) is a biodegradable polymer and can be obtained from renewable sources such as corn starch. It has a wide range of applications, such as in food packaging and tissue engineering. PLA is also of interest in drug delivery application because it can degrade into bioabsorbable products in physiological environments. Its degradation mainly comes from the cleavage of its ester groups, and is sensitive to chemical hydrolysis. In polymeric drug delivery system, drugs are encapsulated in polymer. As the polymer degrades, the drugs are released, and the release rate is determined by the polymer degradation rate. Crystallinity of polymer is a factor affecting the degradation rate. A good review on the effect of crystallinity on degradation and drug release can be found in [1]. In general, less crystallinity accelerates degradation and drug release rate. To create polymeric drug delivery system, drug molecules are dispersed or dissolved in the polymeric solution, formed through melting the polymer or dissolving it in a solvent. During the process the polymer may crystallize. The crystal structure also influences the degradation rate. Tsuji and Ikada [2] studied the hydrolysis of PLA films and proposed that it begins in the amorphous region between the crystalline lamellae, followed by the disorientation of the lamellae and disappearance of the spherulitic structure.

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“…Cotton et al 58 suggested that c* does not occur at a single and well-defined polymer concentration since there is a gradual change in the radius of gyration (R g ) in the dilute region, and proposed that c* should be located between two limits defined by,…”

Section: Determination Of Theoretical C* For Star Polymersmentioning

confidence: 99%

Bimolecular radical termination: New perspectives and insights

Johnston‐Hall

Monteiro

2008

J. Polym. Sci. A Polym. Chem.

133

216

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ABSTRACT:The reversible addition-fragmentation chain transfer-chain length dependent termination (RAFT-CLD-T) method has allowed us to answer a number of fundamental questions regarding the mechanism of diffusion-controlled bimolecular termination in free-radical polymerization (FRP). We carried out RAFTmediated polymerizations of methyl acrylate (MA) in the presence of a star matrix to develop an understanding of the effect of polymer matrix architecture on the termination of linear polyMA radicals and compared this to polystyrene, polymethyl methacrylate, and polyvinyl acetate systems. It was found that the matrix architecture had little or no influence on termination in the dilute regime.However, due to the smaller hydrodynamic volumes of the stars in solution compared to linear polymer of the same molecular weight, the gel onset point occurred at greater conversions, and supported the postulate that chain overlap (or c*) is the main cause for the observed autoacceleration observed in FRP. Other theories based on \short-long" termination or free-volume should be disregarded. Additionally, since our systems are well below the entanglement molecular weight, entanglements should also be disregarded as the cause of the gel onset. The semidilute regime occurs over a small conversion range and is difficult to quantify. However, we obtain accurate dependencies for termination in the concentrated regime, and observed that the star polymers (through the tethering of the arms) provided constriction points in the matrix that significantly slow the diffusion of linear polymeric radicals. Although, this could at first sight be postulated to be due to reptation, the dependencies showed that reptation could be considered only at very high conversions (close to the glass transition regime). In general, we find from our data that the polymer matrix is much more mobile than what is expected if reptation were to dominate.

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Experimental determination of the temperature–concentration diagram of flexible polymer solutions by neutron scattering

Cited by 183 publications

References 16 publications

Monte Carlo simulations of densely-packed athermal polymers in the bulk and under confinement

Monte Carlo simulations of densely-packed athermal polymers in the bulk and under confinement

Effect of Film Formation Method and Annealing on Crystallinity of Poly(L-Lactic Acid) Films

Bimolecular radical termination: New perspectives and insights

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