The Mechanism of Modifier Action in GR-S Polymerization. II

Abstract The chain transfer theory of modifier action has been tested on commercial GR-S by means of molecular weight and sulfur content determination. The number of sulfur atoms per molecule was found to range between 0.7 and 1.1, to be compared to the theoretical value of unity. In view of the experimental difficulties involved, the results are considered to be in good agreement with the theory.

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Molecular Weight Evolution in the Catalytic Chain Transfer Polymerization of CO2-Expanded Methyl Methacrylate

Macromolecules ◽

10.1021/ma8000737 ◽

2008 ◽

Vol 41 (14) ◽

pp. 5141-5147 ◽

Cited By ~ 8

Author(s):

Grzegorz Zwolak ◽

Frank P. Lucien

Keyword(s):

Molecular Weight ◽

Methyl Methacrylate ◽

Chain Transfer ◽

Catalytic Chain Transfer ◽

Chain Transfer Polymerization

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Nano-Assemblies from Amphiphilic PnBA-b-POEGA Copolymers as Drug Nanocarriers

Polymers ◽

10.3390/polym13071164 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1164

Author(s):

Angeliki Chroni ◽

Thomas Mavromoustakos ◽

Stergios Pispas

Keyword(s):

Molecular Weight ◽

Chain Transfer ◽

Raft Polymerization ◽

Polymeric Nanocarriers ◽

Reversible Addition ◽

2D Noesy ◽

Drug Nanocarriers ◽

Glycol Methyl Ether ◽

Different Molecular Weight

The focus of this study is the development of highly stable losartan potassium (LSR) polymeric nanocarriers. Two novel amphiphilic poly(n-butyl acrylate)-block-poly(oligo(ethylene glycol) methyl ether acrylate) (PnBA-b-POEGA) copolymers with different molecular weight (Mw) of PnBA are synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization, followed by the encapsulation of LSR into both PnBA-b-POEGA micelles. Based on dynamic light scattering (DLS), the PnBA30-b-POEGA70 and PnBA27-b-POEGA73 (where the subscripts denote wt.% composition of the components) copolymers formed micelles of 10 nm and 24 nm in water. The LSR-loaded PnBA-b-POEGA nanocarriers presented increased size and greater mass nanostructures compared to empty micelles, implying the successful loading of LSR into the inner hydrophobic domains. A thorough NMR (nuclear magnetic resonance) characterization of the LSR-loaded PnBA-b-POEGA nanocarriers was conducted. Strong intermolecular interactions between the biphenyl ring and the butyl chain of LSR with the methylene signals of PnBA were evidenced by 2D-NOESY experiments. The highest hydrophobicity of the PnBA27-b-POEGA73 micelles contributed to an efficient encapsulation of LSR into the micelles exhibiting a greater value of %EE compared to PnBA30-b-POEGA70 + 50% LSR nanocarriers. Ultrasound release profiles of LSR signified that a great amount of the encapsulated LSR is strongly attached to both PnBA30-b-POEGA70 and PnBA27-b-POEGA73 micelles.

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Self-Stable Precipitation Polymerization Molecular Entanglement Effect and Molecular Weight Simulations and Experiments

Polymers ◽

10.3390/polym13142243 ◽

2021 ◽

Vol 13 (14) ◽

pp. 2243

Author(s):

Jiali Qu ◽

Yi Gao ◽

Wantai Yang

Keyword(s):

Molecular Weight ◽

Maleic Anhydride ◽

Molecular Conformation ◽

Average Molecular Weight ◽

Precipitation Polymerization ◽

Radius Of Gyration ◽

Propagation Mechanism ◽

Reactive Molecular Dynamics ◽

End Distance ◽

Good Agreement

In this paper, we developed a reactive molecular dynamics (RMD) scheme to simulate the Self-Stable Precipitation (SP) polymerization of 1-pentene and cyclopentene (C5) with maleic anhydride (MAn) in an all-atom resolution. We studied the chain propagation mechanism by tracking the changes in molecular conformation and analyzing end-to-end distance and radius of gyration. The results show that the main reason of chain termination in the reaction process was due to intramolecular cyclic entanglement, which made the active center wrapped in the center of the globular chain. After conducting the experiment in the same condition with the simulation, we found that the distribution trend and peak value of the molecular-weight-distribution curve in the simulation were consistent with experimental results. The simulated number average molecular weight (Mn) and weight average molecular weight (Mw) were in good agreement with the experiment. Moreover, the simulated molecular polydispersity index (PDI) for cyclopentene reaction with maleic anhydride was accurate, differing by 0.04 from the experimental value. These show that this model is suitable for C5–maleic anhydride self-stable precipitation polymerization and is expected to be used as a molecular weight prediction tool for other maleic anhydride self-stable precipitation polymerization system.

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Cationic Copolymerization of Isobutylene with 4-Vinylbenzenecyclobutylene: Characteristics and Mechanisms

Polymers ◽

10.3390/polym12010201 ◽

2020 ◽

Vol 12 (1) ◽

pp. 201 ◽

Cited By ~ 1

Author(s):

Zhifei Chen ◽

Shuxin Li ◽

Yuwei Shang ◽

Shan Huang ◽

Kangda Wu ◽

...

Keyword(s):

Mechanical Properties ◽

Molecular Weight ◽

Cationic Polymerization ◽

Transfer Reaction ◽

Chain Transfer ◽

Solid Phase ◽

Random Copolymer ◽

Glass Transition Temperatures ◽

Cationic Copolymerization ◽

Chain Transfer Reaction

A random copolymer of isobutylene (IB) and 4-vinylbenzenecyclobutylene (4-VBCB) was synthesized by cationic polymerization at −80 °C using 2-chloro-2,4,4-trimethylpentane (TMPCl) as initiator. The laws of copolymerization were investigated by changing the feed quantities of 4-VBCB. The molecular weight of the copolymer decreased, and its molecular weight distribution (MWD) increased with increasing 4-VBCB content. We proposed a possible copolymerization mechanism behind the increase in the chain transfer reaction to 4-VBCB with increasing of feed quantities of 4-VBCB. The thermal properties of the copolymers were studied by solid-phase heating and crosslinking. After crosslinking, the decomposition and glass transition temperatures (Tg) of the copolymer increased, the network structure that formed did not break when reheated, and the mechanical properties remarkably improved.

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