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Zhao-yan Sun - One of the best experts on this subject based on the ideXlab platform.
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Effects of Copolymer Composition and Subphase pH/Temperature on the Interfacial Aggregation Behavior of Poly(2-(dimethylamino)ethyl methacrylate)-block-poly(lauryl methacrylate)
The Journal of Physical Chemistry C, 2020Co-Authors: Hongxu Chen, Gangyao Wen, Varvara Chrysostomou, Stergios Pispas, Wenting Pan, Jintao Zuo, Zhao-yan SunAbstract:The Langmuir film balance technique was used to investigate the effects of Copolymer Composition and subphase pH/temperature on the aggregation behaviors of two stimuli-responsive amphiphilic diblo...
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effects of Copolymer Composition and subphase ph temperature on the interfacial aggregation behavior of poly 2 dimethylamino ethyl methacrylate block poly lauryl methacrylate
The Journal of Physical Chemistry, 2020Co-Authors: Hongxu Chen, Gangyao Wen, Varvara Chrysostomou, Stergios Pispas, Wenting Pan, Jintao Zuo, Zhao-yan SunAbstract:The Langmuir film balance technique was used to investigate the effects of Copolymer Composition and subphase pH/temperature on the aggregation behaviors of two stimuli-responsive amphiphilic diblock Copolymers poly(2-(dimethylamino)ethyl methacrylate)-block-poly(lauryl methacrylate) (PDMAEMA-b-PLMA) at the air/water interface. The morphologies of their Langmuir–Blodgett (LB) films were characterized by atomic force microscopy. With the rise in subphase pH, the corresponding surface pressure–molecular area isotherms of the two Copolymers gradually move to large areas due to the decreased protonation degrees of PDMAEMA blocks. Almost all the LB films of the predominantly hydrophilic Copolymer prepared under different subphase conditions exhibit isolated circular micelles. For the predominantly hydrophobic Copolymer, however, the dense wormlike aggregates and the large domains appear in its LB films due to the connection of adjacent PLMA cores at low temperature and the local richness of PDMAEMA chains at high temperature, respectively.
Christopher Barner-kowollik - One of the best experts on this subject based on the ideXlab platform.
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Reversible addition fragmentation chain transfer Copolymerization: influence of the RAFT process on the Copolymer Composition
Polymer, 2004Co-Authors: Achim Feldermann, Andrew Ah Toy, Hong Phan, Martina H. Stenzel, Thomas P. Davis, Christopher Barner-kowollikAbstract:Abstract Reversible addition fragmentation chain transfer (RAFT) mediated and conventional Copolymerizations at low monomer conversions have been carried out for the systems methyl methacrylate (MMA)-styrene, methyl acrylate (MA)-styrene and methyl methacrylate-butyl acrylate (BA). The polymer samples have been analyzed via 1H-NMR spectroscopy to obtain the Copolymer Composition and the terminal model reactivity ratios. In the RAFT mediated Copolymerizations, the polymer mole fraction of the monomer with the larger reactivity ratio is increased compared to the conventional Copolymerization. Simulations have been carried out using the program package PREDICI® to examine possible explanations for the experimental findings. The simulations demonstrate that the RAFT process itself may alter the macroradical populations and the Copolymer Composition by offering additional reaction pathways. Further, the rate coefficients for the initiation reaction and the pre-equilibrium play an important role in determining the Copolymer Composition. The rate coefficients governing the main equilibrium of the RAFT process have only a minor impact on the Copolymer Composition.
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Reversible addition fragmentation chain transfer Copolymerization: Influence of the RAFT process on the Copolymer Composition
2004Co-Authors: Achim Feldermann, Andrew Ah Toy, Hong Phan, Martina H. Stenzel, Thomas P. Davis, Christopher Barner-kowollikAbstract:Reversible addition fragmentation chain transfer (RAFT) mediated and conventional Copolymerizations at low monomer conversions have been carried out for the systems methyl methacrylate (MMA)-styrene, methyl acrylate (MA)-styrene and methyl methacrylate-butyl acrylate (BA). The polymer samples have been analyzed via 1H-NMR spectroscopy to obtain the Copolymer Composition and the terminal model reactivity ratios. In the RAFT mediated Copolymerizations, the polymer mole fraction of the monomer with the larger reactivity ratio is increased compared to the conventional Copolymerization. Simulations have been carried out using the program package PREDICI ® to examine possible explanations for the experimental findings. The simulations demonstrate that the RAFT process itself may alter the macroradical populations and the Copolymer Composition by offering additional reaction pathways. Further, the rate coefficients for the initiation reaction and the pre-equilibrium play an important role in determining the Copolymer Composition. The rate coefficients governing the main equilibrium of the RAFT process have only a minor impact on the Copolymer Composition. © 2004 Elsevier Ltd. All rights reserved.
René Holm - One of the best experts on this subject based on the ideXlab platform.
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Influence of PVP/VA Copolymer Composition on drug-polymer solubility.
European journal of pharmaceutical sciences : official journal of the European Federation for Pharmaceutical Sciences, 2016Co-Authors: Malte Bille Rask, Matthias Manne Knopp, René Holm, Niels Erik Olesen, Thomas RadesAbstract:In this study, the influence of Copolymer Composition on drug-polymer solubility was investigated. The solubility of the model drug celecoxib (CCX) in various polyvinylpyrrolidone/vinyl acetate (PVP/VA) Copolymer Compositions (70/30, 60/40, 50/50 and 30/70 w/w) and the pure homopolymers polyvinylpyrrolidone (PVP) and polyvinyl acetate (PVA) was predicted at 25 °C using a thermal analysis method based on the recrystallization of a supersaturated amorphous dispersion (recrystallization method). These solubilities were compared with a prediction based on the solubility of CCX in the liquid monomeric precursors of PVP/VA, N-vinylpyrrolidone (NVP) and vinyl acetate (VA), using the Flory-Huggins lattice theory (liquid monomer solubility approach). The solubilities predicted from the liquid monomer solubility approach increased linearly with increasing VP/VA ratio from 0.03-0.60 w/w. Even though the solubilities predicted from the recrystallization method also increased with increasing VP/VA ratio from 0.02-0.40 w/w, the predicted solubility seemed to approach a plateau at high VP/VA ratios. Increasing positive deviations from the Gordon-Taylor equation with increasing VP/VA ratio indicated strong interactions between CCX and the VP repeat unit, which was in accordance with the relatively high solubilities predicted using both methods. As the solubility plateau may be a consequence of steric hindrance caused by the size differences between CCX and the VP repeat units, it is likely that a CCX molecule interacting with a VP repeat unit hinders another CCX molecule from binding to the neighboring repeat units in the polymer chain. Therefore, it is possible that replacing these neighboring hygroscopic VP repeat units with hydrophobic VA repeat units, could increase the physical stability of an amorphous solid dispersion without compromising the drug-polymer solubility. This knowledge could be used advantageously in future development of amorphous drug delivery systems as Copolymers could be customized to provide optimal drug-polymer solubility and physical stability.
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Influence of Copolymer Composition on In Vitro and In Vivo Performance of Celecoxib-PVP/VA Amorphous Solid Dispersions
The AAPS journal, 2016Co-Authors: Matthias Manne Knopp, Julia Hoang Nguyen, Peter Langguth, Thomas Rades, René HolmAbstract:Previous studies suggested that an amorphous solid dispersion with a Copolymer consisting of both hydrophobic and hydrophilic monomers could improve the dissolution profile of a poorly water-soluble drug compared to the crystalline form. Therefore, this study investigated the influence of the Copolymer Composition of polyvinylpyrrolidone/vinyl acetate (PVP/VA) on the non-sink in vitro dissolution behavior and in vivo performance of celecoxib (CCX) amorphous solid dispersions. The study showed that the hydrophilic monomer vinylpyrrolidone (VP) was responsible for the generation of CCX supersaturation whereas the hydrophobic monomer vinyl acetate (VA) was responsible for the stabilization of the supersaturated solution. For CCX, there was an optimal Copolymer Composition around 50–60% VP content where further replacement of VP monomers with VA monomers did not have any biopharmaceutical advantages. A linear relationship was found between the in vitro AUC0-4h and in vivo AUC0-24h for the CCX:PVP/VA systems, indicating that the non-sink in vitro dissolution method applied in this study was useful in predicting the in vivo performance. These results indicated that when formulating a poorly water-soluble drug as an amorphous solid dispersion using a Copolymer, the Copolymer Composition has a significant influence on the dissolution profile and in vivo performance. Thus, the dissolution profile of a drug can theoretically be tailored by changing the monomer ratio of a Copolymer with respect to the required in vivo plasma-concentration profile. As this ratio is likely to be drug dependent, determining the optimal ratio between the hydrophilic (dissolution enhancing) and hydrophobic (crystallization inhibiting) monomers for a given drug is imperative.
Hongxu Chen - One of the best experts on this subject based on the ideXlab platform.
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Effects of Copolymer Composition and Subphase pH/Temperature on the Interfacial Aggregation Behavior of Poly(2-(dimethylamino)ethyl methacrylate)-block-poly(lauryl methacrylate)
The Journal of Physical Chemistry C, 2020Co-Authors: Hongxu Chen, Gangyao Wen, Varvara Chrysostomou, Stergios Pispas, Wenting Pan, Jintao Zuo, Zhao-yan SunAbstract:The Langmuir film balance technique was used to investigate the effects of Copolymer Composition and subphase pH/temperature on the aggregation behaviors of two stimuli-responsive amphiphilic diblo...
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effects of Copolymer Composition and subphase ph temperature on the interfacial aggregation behavior of poly 2 dimethylamino ethyl methacrylate block poly lauryl methacrylate
The Journal of Physical Chemistry, 2020Co-Authors: Hongxu Chen, Gangyao Wen, Varvara Chrysostomou, Stergios Pispas, Wenting Pan, Jintao Zuo, Zhao-yan SunAbstract:The Langmuir film balance technique was used to investigate the effects of Copolymer Composition and subphase pH/temperature on the aggregation behaviors of two stimuli-responsive amphiphilic diblock Copolymers poly(2-(dimethylamino)ethyl methacrylate)-block-poly(lauryl methacrylate) (PDMAEMA-b-PLMA) at the air/water interface. The morphologies of their Langmuir–Blodgett (LB) films were characterized by atomic force microscopy. With the rise in subphase pH, the corresponding surface pressure–molecular area isotherms of the two Copolymers gradually move to large areas due to the decreased protonation degrees of PDMAEMA blocks. Almost all the LB films of the predominantly hydrophilic Copolymer prepared under different subphase conditions exhibit isolated circular micelles. For the predominantly hydrophobic Copolymer, however, the dense wormlike aggregates and the large domains appear in its LB films due to the connection of adjacent PLMA cores at low temperature and the local richness of PDMAEMA chains at high temperature, respectively.
Achim Feldermann - One of the best experts on this subject based on the ideXlab platform.
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Reversible addition fragmentation chain transfer Copolymerization: influence of the RAFT process on the Copolymer Composition
Polymer, 2004Co-Authors: Achim Feldermann, Andrew Ah Toy, Hong Phan, Martina H. Stenzel, Thomas P. Davis, Christopher Barner-kowollikAbstract:Abstract Reversible addition fragmentation chain transfer (RAFT) mediated and conventional Copolymerizations at low monomer conversions have been carried out for the systems methyl methacrylate (MMA)-styrene, methyl acrylate (MA)-styrene and methyl methacrylate-butyl acrylate (BA). The polymer samples have been analyzed via 1H-NMR spectroscopy to obtain the Copolymer Composition and the terminal model reactivity ratios. In the RAFT mediated Copolymerizations, the polymer mole fraction of the monomer with the larger reactivity ratio is increased compared to the conventional Copolymerization. Simulations have been carried out using the program package PREDICI® to examine possible explanations for the experimental findings. The simulations demonstrate that the RAFT process itself may alter the macroradical populations and the Copolymer Composition by offering additional reaction pathways. Further, the rate coefficients for the initiation reaction and the pre-equilibrium play an important role in determining the Copolymer Composition. The rate coefficients governing the main equilibrium of the RAFT process have only a minor impact on the Copolymer Composition.
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Reversible addition fragmentation chain transfer Copolymerization: Influence of the RAFT process on the Copolymer Composition
2004Co-Authors: Achim Feldermann, Andrew Ah Toy, Hong Phan, Martina H. Stenzel, Thomas P. Davis, Christopher Barner-kowollikAbstract:Reversible addition fragmentation chain transfer (RAFT) mediated and conventional Copolymerizations at low monomer conversions have been carried out for the systems methyl methacrylate (MMA)-styrene, methyl acrylate (MA)-styrene and methyl methacrylate-butyl acrylate (BA). The polymer samples have been analyzed via 1H-NMR spectroscopy to obtain the Copolymer Composition and the terminal model reactivity ratios. In the RAFT mediated Copolymerizations, the polymer mole fraction of the monomer with the larger reactivity ratio is increased compared to the conventional Copolymerization. Simulations have been carried out using the program package PREDICI ® to examine possible explanations for the experimental findings. The simulations demonstrate that the RAFT process itself may alter the macroradical populations and the Copolymer Composition by offering additional reaction pathways. Further, the rate coefficients for the initiation reaction and the pre-equilibrium play an important role in determining the Copolymer Composition. The rate coefficients governing the main equilibrium of the RAFT process have only a minor impact on the Copolymer Composition. © 2004 Elsevier Ltd. All rights reserved.
