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Tetrablock Copolymers (tetrablock + copolymer)

Distribution by Scientific Domains
Polymers and Materials Science100%

Selected Abstracts

Morphology of ABCD Tetrablock Copolymers Predicted by Self-Consistent Field Theory

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 4 2005
Rong Wang
Abstract Summary: We studied the two-dimensional (2D) microphase-separated morphology of linear ABCD tetrablock copolymers by self-consistent field theory. By varying the interaction parameters and the compositions, we found at least twelve structures, two of which , "four-color" lamellae and "three-color" core-shell hexagonal phase , prove the existing experimental observations. These morphologies were discussed in correlation with the volume fraction of the components and the interaction parameters. A specific behavior of symmetrical tetrablock copolymers, i.e., fA,=,fD and fB,=,fC, is that the stable phases are lamellae, which is different from symmetrical ABC triblock copolymer having order-to-order transition. These results are helpful for the design of new block copolymer-based nanomaterials. [source]

Cancer-associated pH-responsive tetracopolymeric micelles composed of poly(ethylene glycol)- b -poly(L -histidine)- b -poly(L -lactic acid)- b -poly(ethylene glycol)

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2008
Kyung Taek Oh
Abstract To create a novel vector for specifically delivering anticancer therapy to solid tumors, we used diafiltration to synthesize pH-sensitive polymeric micelles. The micelles, formed from a tetrablock copolymer [poly(ethylene glycol) -b -poly(L -histidine)- b -poly(L -lactic acid)- b -poly(ethylene glycol)] consisted of a hydrophobic poly(L -histidine) (polyHis) and poly(L -lactic acid) (PLA) core and a hydrophilic poly(ethylene glycol) (PEG) shell, in which we encapsulated the model anticancer drug doxorubicin (DOX). The robust micelles exhibited a critical micellar concentration (CMC) of 2.1,3.5,µg/ml and an average size of 65,80,nm pH 7.4. Importantly, they showed a pH-dependent micellar destabilization, due to the concurrent ionization of the polyHis and the rigidity of the PLA in the micellar core. In particular, the molecular weight of PLA block affected the ionization of the micellar core. Depending on the molecular weight of the PLA block, the micelles triggering released DOX at pH 6.8 (i.e. cancer acidic pH) or pH 6.4 (i.e. endosomal pH), making this system a useful tool for specifically treating solid cancers or delivering cytoplasmic cargo in vivo. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Synthesis of Comb Tri- and Tetrablock Copolymers Catalyzed by the Grubbs First Generation Catalyst

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 16 2009
M. Brett Runge
Abstract High molecular weight tri- and tetrablock copolymers were synthesized from the commercially available Grubbs first generation catalyst for the first time. These polymers had degrees of polymerization from 430 to 1,100, molecular weights up to 419,000 g,·,mol,1, and narrow polydispersities. Oxanorbornene monomers were chosen due to their fast rates of polymerization and slow rates of cross metathesis. Polystyrene arms were grown from selected blocks by atom transfer radical polymerization to yield architecturally complex comb tri- and tetrablock copolymers. These polymers self-assembled in the solid state into ordered morphologies that were characterized by scanning electron microscopy. [source]

Morphology of ABCD Tetrablock Copolymers Predicted by Self-Consistent Field Theory

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 4 2005
Rong Wang
Abstract Summary: We studied the two-dimensional (2D) microphase-separated morphology of linear ABCD tetrablock copolymers by self-consistent field theory. By varying the interaction parameters and the compositions, we found at least twelve structures, two of which , "four-color" lamellae and "three-color" core-shell hexagonal phase , prove the existing experimental observations. These morphologies were discussed in correlation with the volume fraction of the components and the interaction parameters. A specific behavior of symmetrical tetrablock copolymers, i.e., fA,=,fD and fB,=,fC, is that the stable phases are lamellae, which is different from symmetrical ABC triblock copolymer having order-to-order transition. These results are helpful for the design of new block copolymer-based nanomaterials. [source]