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Anionic Micelle-Forming Triblock Copolymers as Nanocontainers for Doxorubicin  [cached]
Kunitskaya L.R.,Stoika R.S.,Shlyakhtina Ye.A.,Zheltonozhskaya T.B.
Proceedings of the International Conference Nanomaterials : Applications and Properties , 2012,
Abstract: The anionic derivative of asymmetric triblock copolymer containing biocompatible chemically complementary polyacrylamide and poly(ethylene oxide) (PAAm-b-PEO-b-PAAm) was obtained. The micellization of the initial (TBC) and modified (TBC-COOH) copolymer samples in aqueous solution were investigated. Practically the same values of the critical micellization concentration and the Gibbs free micellization energy for both TBCs were found. The anticancer effects of the doxorubicin (DOX)-loaded micelles of the initial and modified triblock copolymers were studied on the tumor cells of human T-leukemia of Jurkat line, transformed leukemia of L929 line and mouse lymphatic leukemia of L1210 line. The fact of high efficacy of DOX/TBC and DOX/TBC-COOH compositions in compare with pure DOX was determined and discussed.
The non-centrosymmetric lamellar phase in blends of ABC triblock and ac diblock copolymers  [PDF]
Robert A. Wickham,An-Chang Shi
Physics , 2001, DOI: 10.1021/ma010601q
Abstract: The phase behaviour of blends of ABC triblock and ac diblock copolymers is examined using self-consistent field theory. Several equilibrium lamellar structures are observed, depending on the volume fraction of the diblocks, phi_2, the monomer interactions, and the degrees of polymerization of the copolymers. For segregations just above the order-disorder transition the triblocks and diblocks mix together to form centrosymmetric lamellae. As the segregation is increased the triblocks and diblocks spatially separate either by macrophase-separating, or by forming a non-centrosymmetric (NCS) phase of alternating layers of triblock and diblock (...ABCcaABCca...). The NCS phase is stable over a narrow region near phi_2=0.4. This region is widest near the critical point on the phase coexistence curve and narrows to terminate at a triple point at higher segregation. Above the triple point there is two-phase coexistence between almost pure triblock and diblock phases. The theoretical phase diagram is consistent with experiments.
Weak Segregation Theory and Non-Conventional Morphologies in the Ternary ABC Triblock Copolymers  [PDF]
Igor Ya. Erukhimovich
Physics , 2005, DOI: 10.1140/epje/e2005-00054-5
Abstract: The Leibler weak segregation theory in molten diblock copolymers is generalized with due regard for the 2nd shell harmonics contributions defined in the paper and the phase diagrams are built for the linear and miktoarm ternary ABC triblock copolymers. The symmetric linear copolymers with the middle block non-selective with respect to the side ones are shown to undergo the continuous ODT not only into the lamellar phase but also into various non-conventional cubic phases (depending on the middle block composition it could be the simple cubic, face-centered cubic or non-centrosymmetric phase revealing the symmetry of space group No.214 first predicted to appear in molten block copolymers). For asymmetric linear ABC copolymers a region of compositions is found where the weakly segregated gyroid (double gyroid) phase exists between the planar hexagonal and lamellar or one of the non-conventional cubic phases up to the very critical point. In contrast, the miktoarm ABC block copolymers with one of its arm non-selective with respect to the two others are shown to reveal a pronounced tendency towards strong segregation, which is preceded by increase of stability of the conventional BCC phase and a peculiar weakly segregated BCC phase (BCC3), where the dominant harmonics belong to the 3rd co-ordination sphere of the reciprocal lattice. The validity region of the developed theory is discussed and outlined in the composition triangles both for linear and miktoarm copolymers.
SELF-ASSEMBLY OF TRIBLOCK COPOLYMERS IN AQUEOUS SOLUTION
URBANO,BRUNO; SILVA,PATRICIO; OLEA,ANDRéS F; FUENTES,IRMA; MARTINEZ,FRANCISCO;
Journal of the Chilean Chemical Society , 2008, DOI: 10.4067/S0717-97072008000200013
Abstract: the aggregation of pe4vp-b-ps-b-pe4vp block copolymers was studied in aqueous solution. triblock copolymers p4vp-b-ps-b-p4vp were synthesized by sequential anionic polymerization of poly(styrene) and poly(4-vinylpirydine) using sodium naphthalene as a bifunctional initiator. subsequently, the 4-vinylpyridine units were quaternized with ethyl bromide to obtain cationic pe4vp-b-ps-b-pe4vp block copolymers. both star and crew-cut micelles were formed. the concentrations at which micelles are formed cmc were determined, by steady-state and time-resolved fluorescence probing methods, as a function of quatemization degree. the results indicate that cmc of crew-cut micelles increases with increasing charge density of the pe4vp blocks. for star micelles there is not a clear dependency of cmc with the percentage of quatemization. the lifetime of pyrene fluorescence and the ratio i1/i3 were determined at concentrations of copolymers well above the cmc, and the results show that the location of pyrene into the micelle changes with the charge density of the micelle corona. the micropolarity sensed by pyrene decreases with increasing quatemization degree. the presence of aggregates was confirmed by transmission electronic microscopy.
SELF-ASSEMBLY OF TRIBLOCK COPOLYMERS IN AQUEOUS SOLUTION  [cached]
BRUNO URBANO,PATRICIO SILVA,ANDRéS F OLEA,IRMA FUENTES
Journal of the Chilean Chemical Society , 2008,
Abstract: The aggregation of PE4VP-b-PS-b-PE4VP block copolymers was studied in aqueous solution. Triblock copolymers P4VP-b-PS-b-P4VP were synthesized by sequential anionic polymerization of poly(styrene) and poly(4-vinylpirydine) using sodium naphthalene as a bifunctional initiator. Subsequently, the 4-vinylpyridine units were quaternized with ethyl bromide to obtain cationic PE4VP-b-PS-b-PE4VP block copolymers. Both star and crew-cut micelles were formed. The concentrations at which micelles are formed cmc were determined, by steady-state and time-resolved fluorescence probing methods, as a function of quatemization degree. The results indicate that cmc of crew-cut micelles increases with increasing charge density of the PE4VP blocks. For star micelles there is not a clear dependency of cmc with the percentage of quatemization. The lifetime of pyrene fluorescence and the ratio I1/I3 were determined at concentrations of copolymers well above the cmc, and the results show that the location of pyrene into the micelle changes with the charge density of the micelle corona. The micropolarity sensed by pyrene decreases with increasing quatemization degree. The presence of aggregates was confirmed by transmission electronic microscopy.
Reversible Gel Formation of Triblock Copolymers Studied by Molecular Dynamics Simulation  [PDF]
Lei Guo,Erik Luijten
Physics , 2004, DOI: 10.1002/polb.20386
Abstract: Molecular dynamics simulations have been employed to study the formation of a physical (thermoreversible) gel by amphiphilic A-B-A triblock copolymers in aqueous solution. In order to mimic the structure of hydrogel-forming polypeptides employed in experiments [W.A. Petka et al., Science 281, 389 (1998)], the endblocks of the polymer chains are modeled as hydrophobic rods representing the alpha-helical part of the polypeptides whereas the central B-block is hydrophilic and semi-flexible. We have determined structural properties, such as the hydrophobic cluster-size distribution function, the geometric percolation point and pair correlation functions, and related these to the dynamical properties of the system. Upon decrease of the temperature, a network structure is formed in which bundles of endblocks act as network junctions. Both at short and medium distances an increased ordering is observed, as characterized by the pair correlation function. Micelle formation and the corresponding onset of geometric percolation induce a strong change in dynamical quantities, e.g., in the diffusion constant and the viscosity, and causes the system to deviate from the Stokes-Einstein relation. The dynamical properties show a temperature dependence that is strongly reminiscent of the behavior of glass-forming liquids. The appearance of a plateau in the stress autocorrelation function suggests that the system starts to exhibit a solid-like response to applied stress once the network structure has been formed, although the actual sol-gel transition occurs only at a considerably lower temperature.
Micelles of Amphiphilic Diblock and Triblock Copolymers Based on Poly(ethylene oxide) and Poly(e-caprolactone) and Their Potential as Nanocontainers for Drugs  [cached]
Partsevskaya S.,Klymchuk D.O.,Zheltonozhskaya T.B.,Gorchev V.F.
Proceedings of the International Conference Nanomaterials : Applications and Properties , 2012,
Abstract: The development and usage of nanoscaled carriers for effective delivery of toxic and insoluble drugs is of particular interest in recent years. One of the most convenient ways to create such therapeutic systems is self-assembling of amphiphilic block copolymers with immiscible biocompatible and biodegradable components, for example polyethers and polyesters. Two series of MOPEO-b-PCL diblock copolymers (DBCs) contained methoxypoly(ethylene oxide) (Mn = 2.5 and 4.54 kDa) and poly(ε-caprolactone) of a variable Mn and also the triblock copolymer (TBC) PCL-b-PEO-b-PCL based on poly(ethylene oxide) (Mv = 6 kDa) were synthesized and characterized by NMR spectroscopy. Their micellization in water/dioxane solutions was studied using static and dynamic light scattering, UV-Vis spectroscopy and TEM. The micelles of spherical and ellipsoidal morphology, which size and stability in a solution (estimated by CMC and - G values) grew with increase in the length of both the “core”-forming (PCL) and “corona”-forming (PEO) blocks, were found in the dilute DBC solutions. Unlike this, the “flower-like” micelles of a smallest size (66 nm) and stability formed in TBC solutions. The prospects for application of DBC and TBC micelles as biocompatible and biodegradable carriers for poorly soluble and anticancer drugs (prednisolon, doxorubicin etc.) were considered.
Aggregation number distributions and mesoglobules in dilute solutions of diblock and triblock copolymers  [PDF]
E. G. Timoshenko,Yu. A. Kuznetsov
Physics , 2000, DOI: 10.1209/epl/i2001-00156-5
Abstract: We investigate the aggregation number and size distributions for inter-molecular clusters of amphiphilic diblock and triblock copolymers in poor solvent at very low concentrations. Diblocks and triblocks with hydrophilic ends are shown to possess narrow distributions corresponding to formation of monodispersed mesoglobules. Diblocks with hydrophobic ends are found to produce inter-cluster multimers due to bridging by the hydrophilic middle blocks, resulting in polydisperse distributions. Implications of these observations for preparation of monodispersed nanoparticles and, potentially, understanding of the quaternary structure of proteins are discussed.
Smectic ordering in athermal systems of rod-like triblock copolymers  [PDF]
Szabolcs Varga,Seth Fraden
Physics , 2007, DOI: 10.1063/1.2787009
Abstract: The phase behavior of the system of parallel rigid triblock copolymers is examined using the second-virial density functional theory. The triblock particle consists of two identical infinitely thin hard rods of finite lengths on the opposite ends of one central hard cylinder with nonzero length and diameter. Stability analyses and free energy calculations show that the system of parallel particles can form not only uniform nematic and smectic A phases, but a smectic-C phase too. The stability and structure of the tilted structure is controlled by only the diameter and the length of the central cylinder segment. Interestingly, the diameter effects only the layer tilting and the periodicity, but not the packing fraction of the nematic to smectic-C transition. For all values of cylinder length the usual smectic-A and smectic-C transitions compete with each other and no nematic-columnar transition is observed. At low and high cylinder length the smectic-A phase is stabilized first, while the smectic C is the most stable for intermediate length values.
Electronic confinement in quasi-one-dimensional triblock copolymers
Electronic confinement in quasi—one—dimensional triblock copolymers

Liu De-Sheng,Wang Lu-Xi,Xie Shi-Jie,Han Sheng-Hao,Mei Liang-Mo,
刘德胜
,王鹿霞,解士杰,韩圣浩,梅良模

中国物理 B , 2003,
Abstract: A tight-binding calculation to describe the triblock copolymer xPA(polyacetylene)/nPPP (poly(p-phenylene))/yPA or xPPP/nPA/yPPP is presented. The interfacial coupling between homopolymer segments is attributed to the hopping of π-electrons and the coupling of σ-bonds. The dependence of the band gap of triblock copolymers on the interfacial couplings or on the composite segment lengths is studied. The influence of composite segment lengths on the electron density is also studied. For nPPP/xPA/nPPP structures, the band gap varies with PA segment length over a wide range of 1.32-2.74eV. For nPA/xPPP/nPA structures,the band gap is invariant with PPP segment length. It is found that a spontaneous tunnelling phenomenon could take place in nPA/xPPP/nPA structures. Furthermore, the polaron caused by doping an electron into nPA/xPPP/nPA will tend to be confined in one of the well (PA) parts. This kind of confinement may increase the electron-hole recombination probability.
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