scholarly journals Mechanical and Morphological Properties of Waterborne ABA Hard-Soft-Hard Block Copolymers Synthesized by Means of RAFT Miniemulsion Polymerization

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1259 ◽  
Author(s):  
Gordana Siljanovska Petreska ◽  
Arantxa Arbe ◽  
Clemens Auschra ◽  
Maria Paulis
Keyword(s):  
Molecular Weight ◽  
Block Copolymers ◽  
Film Formation ◽  
Miniemulsion Polymerization ◽  
Morphological Properties ◽  
Phase System ◽  
Two Phase ◽  
Raft Agent ◽  
Different Temperatures ◽  
Equilibrium Morphology

High molecular weight waterborne ABA block copolymers of styrene (St) and 2-ethylhexyl acrylate (2EHA) containing hard and soft domains were synthesized by means of RAFT (mini)emulsion polymerization using a bifunctional symmetric S,S-dibenzyl trithiocarbonate (DBTTC) RAFT agent. Miniemulsion polymerization was initially used for the synthesis of the A-block, which forms hard domains, followed by 2EHA pre-emulsion feeding to build the B-block soft domains. Polymerization kinetics and the evolution of the Molecular Weight Distribution (MWD) were followed during the synthesis of different ABA block copolymers. The thermal properties of the final symmetric block copolymers were studied on dried films by means of DSC. It was found that the block copolymers have two glass transitions, which indicates the presence of a two-phase system. Phase separation was investigated by means of microscopic techniques (AFM and TEM) and SAXS, both of the particles in the latex form, as well as after film formation at room temperature and after different post-treatments. Films were annealed at temperatures well above the glass transition temperature (Tg) of the hard phase to study the bulk morphology of the films after complete particle coalescence. Moreover, for comparison purposes, the films were re-dissolved in THF, and films were again cast directly from the homogeneous THF solutions. As THF is a good solvent for both blocks, such films serve as a reference for the equilibrium morphology. Finally, DMTA studies of the films annealed at different temperatures were performed to correlate the morphology changes with the mechanical properties of the block copolymers.

scholarly journals Design of Waterborne Asymmetric Block Copolymers as Thermoresponsive Materials

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1253
Author(s):  
Gordana Siljanovska Petreska ◽  
Christof van Sluijs ◽  
Clemens Auschra ◽  
Maria Paulis
Keyword(s):  
Mechanical Properties ◽  
Block Copolymers ◽  
Film Formation ◽  
Miniemulsion Polymerization ◽  
Two Phase ◽  
Dsc Measurements ◽  
Reversible Addition ◽  
Raft Agent ◽  
Different Temperatures ◽  
Morphological Differences

AB diblock waterborne copolymers made of styrene (St) and 2-ethylhexyl acrylate (2EHA) were synthesized by means of two-step reversible addition fragmentation chain transfer (RAFT) (mini)emulsion polymerization. Monofunctional asymmetric RAFT agent was used to initiate the polymerization. The hard polystyrene “A” block was synthesized via miniemulsion polymerization followed by 2EHA pre-emulsion feeding to form the soft “B” block. Polymerization kinetics and the evolution of the molecular weight distribution were followed during synthesis of both initial and final block copolymers. DSC measurements of the block copolymers revealed the existence of two glass transition temperatures (Tgs) and thus the occurrence of two-phase systems. Microscopic techniques (atomic force microscopy (AFM) and transmission electron microscopy (TEM)) were used to study the phase separation within the particles in the latex form, after film formation at room temperature cast directly from the latex and after different post-treatments well above the Tg of the hard-polystyrene domains, when complete particle coalescence had occurred. The morphological differences observed after different annealing temperatures were correlated with the mechanical properties analyzed by DMTA measurements. Finally, the differences found in the mechanical properties of the block copolymers annealed at different temperatures were correlated to their heat seal application results.

Optimization of Aqueous Two Phase Extraction of Proteins from Litopenaeus Vannamei Waste by Response Surface Methodology Coupled Multi-Objective Genetic Algorithm

2019 ◽  
Vol 15 (1) ◽  
Author(s):  
P. Saravana Pandian ◽  
S. Sindhanai Selvan ◽  
A. Subathira ◽  
S. Saravanan
Keyword(s):  
Genetic Algorithm ◽  
Molecular Weight ◽  
Response Surface Methodology ◽  
Response Surface ◽  
Litopenaeus Vannamei ◽  
Value Added ◽  
Phase System ◽  
Two Phase ◽  
Multi Objective ◽  
Multi Objective Genetic Algorithm

Abstract Waste generated from industrial processing of seafood is an enormous source of commercially valuable proteins. One among the underutilized seafood waste is shrimp waste, which primarily consists of head and carapace. Litopenaeus vannamei (L. vannamei) is the widely cultivated shrimp in Asia and contributes to 90 % of aggregate shrimp production in the world. This work was focused on extraction as well as purification of value-added proteins from L. vannamei waste in a single step aqueous two phase system (ATPS). Polyethylene glycol (PEG) and trisodium citrate system were chosen for the ATPS owing to their adequate partitioning and less toxic nature. Response surface methodology (RSM) was implemented for the optimization of independent process variables such as PEG molecular weight (2000 to 6000), pH (6 to 8) and temperature (25 to 45 °C). The results obtained from RSM were further validated using a Multi-objective genetic algorithm (MGA). At the optimized condition of PEG molecular weight 2000, pH 8 and temperature 35 °C, maximum partition coefficient and protein yield were found to be 2.79 and 92.37 %, respectively. Thus, L. vannamei waste was proved to be rich in proteins, which could be processed industrially through cost-effective non-polluting ATPS extraction, and RSM coupled MGA could be a potential tool for such process optimization.

Fluorinated amphiphilic block copolymers via RAFT polymerization and their application as surf-RAFT agent in miniemulsion polymerization

RSC Advances ◽  
2015 ◽  
Vol 5 (20) ◽  
pp. 15461-15468 ◽  
Author(s):  
Bishnu P. Koiry ◽  
Arindam Chakrabarty ◽  
Nikhil K. Singha
Keyword(s):  
Block Copolymer ◽  
Block Copolymers ◽  
Ethylene Glycol ◽  
Raft Polymerization ◽  
Miniemulsion Polymerization ◽  
Amphiphilic Block Copolymers ◽  
Poly Ethylene Glycol ◽  
Raft Agent ◽  
Poly Ethylene ◽  
Glycol Methyl Ether

Preparation of an amphiphilic block copolymer (Am-BCP) based on poly(ethylene glycol) methyl ether methacrylate (PEGMA) and heptafluorobutyl acrylate (HFBA) via RAFT polymerization and application of this Am-BCP as surf-RAFT agent for polymerization of styrene.

scholarly journals Synthesis of Poly(lactic acid)-block-poly(N,N-dimethylaminoethyl methacrylate) Copolymers with Controllable Block Structures via Reversible Addition Fragmentation Polymerization from Aminolyzed Poly(lactic acid)

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Wenwen Yu ◽  
Lijing Zhu ◽  
Jiangao Shi ◽  
Cunting Zhao
Keyword(s):  
Lactic Acid ◽  
Block Copolymers ◽  
Raft Polymerization ◽  
Poly Lactic Acid ◽  
Pseudo First Order Reaction ◽  
Oh Groups ◽  
Dimethylaminoethyl Methacrylate ◽  
Reversible Addition ◽  
Raft Agent ◽  
Different Temperatures

Poly(lactic acid)-block-poly(N,N-dimethylaminoethyl methacrylate) (PLA-PDMAEMA) copolymers were synthesized from aminolyzed PLA via reversible addition fragmentation (RAFT) polymerization. PLA undergoes aminolytic degradation with ethylenediamine (EDA). The kinetics of the aminolysis reaction of PLA at different temperatures and EDA concentrations was investigated in detail. The molar masses of products rapidly decreased in the initial stage at low aminolytic degree. Meanwhile, reactive –NH2 and –OH groups were introduced to the end of shorter PLA chains and used as sites to further immobilize the RAFT agent. PLA-PDMAEMA block copolymers were synthesized. A pseudo-first-order reaction kinetics was observed for the RAFT polymerization of PDMAEMA at a low conversion. By controlling the aminolysis reaction of PLA and RAFT polymerization degree of DMAEMA, the length distributions of the PLA and PDMAEMA blocks can be controlled. This method can be extended to more systems to obtain block copolymers with controllable block structure.

Partitioning Behavior of Lysozyme and α-lactalbumin in Aqueous Two-Phase System Formed by Ionic Liquids and Potassium Phosphate

2017 ◽  
Vol 13 (10) ◽  
Author(s):  
Vanessa S. Sampaio ◽  
Renata C. F. Bonomo ◽  
Cristiane M. Veloso ◽  
Rita C. S. Sousa ◽  
Evaldo C. S. Júnior ◽  
...  
Keyword(s):  
Ionic Liquids ◽  
Partition Coefficients ◽  
Potassium Phosphate ◽  
Inorganic Salts ◽  
Phase System ◽  
Two Phase ◽  
Separation Processes ◽  
Different Temperatures ◽  
Aqueous Two Phase Systems ◽  
Increasing Temperature

AbstractNowadays ionic liquids (ILs), because of their “green” characteristics, have been used for analytical and separation processes. Therefore the partitioning of lysozyme and α-lactalbumin using aqueous two-phase systems (ATPSs) composed of an ionic liquid (chloride 1-ethyl-3-methylimidazolium) and inorganic salts (K2HPO4, KH2PO4) was studied. Phase equilibrium diagrams were obtained to explore the effect of the different temperatures (293.15, 303.15, 313.15, and 323.15) K and pH (7.5, 8.0, and 8.5) used for the partitioning studies. For both proteins, partition coefficients decreased with increasing temperature. The pH influenced the partition coefficients of lysozyme and α-lactalbumin. The thermodynamic parameters (ΔH◦, ΔS◦, ΔG◦) indicate thermodynamic differences between the partitioning of lysozyme and α-lactalbumin in this system. The ΔH◦, ΔS◦, and ΔG◦values of the process studied showed that this process is spontaneous. This work demonstrates the possible use of ATPSs with ILs and inorganic salts as a methodology for the partitioning of lysozyme and α-lactalbumin.

Steady Flow and Dynamic Viscosity of Branched Butadiene-Styrene Block Copolymers

1972 ◽  
Vol 45 (4) ◽  
pp. 1005-1014
Author(s):  
G. Kraus ◽  
F. E. Naylor ◽  
K. W. Rollmann
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Block Copolymers ◽  
Steady Flow ◽  
Domain Structure ◽  
Viscoelastic Behavior ◽  
Significant Degree ◽  
Two Phase ◽  
Total Molecular Weight ◽  
Block Structures

Abstract Steady flow and dynamic viscosities were determined for symmetrical linear and star-branched block copolymers of butadiene and styrene above their upper (polystyrene) glass transition. Block structures examined were B-S-B, (B-S-)3, S-B-S, (S-B-)3 and (S-B-)4. At constant molecular weight and total styrene content viscosities were greater for polymers terminating in styrene blocks, irrespective of branching. Branching decreased the viscosity of either polybutadiene-terminated or polystyrene-terminated block polymers, compared at equal Mw. However, comparisons at equal block lengths showed that the length of the terminal blocks, not the total molecular weight, governs the viscoelastic behavior of these polymers to a surprisingly good approximation. This unusual result is rationalized in terms of the two-phase domain structure of these polymers, which persists to a significant degree in the melt. Below the glass transition of the polystyrene blocks the effects of branching were masked by differences in the morphology of the domain structure unrelated to branching.

scholarly journals Response Surface Methodology for the Evaluation of Magnetite Partitioning Behavior in Polyethylene Glycol-Based Aqueous Biphasic System

2019 ◽  
Vol 43 (6) ◽  
pp. 2807-2813 ◽  
Author(s):  
Behnia Shahrokhi ◽  
Mohsen Pirdashti ◽  
Mozhgan Managhebi
Keyword(s):  
Molecular Weight ◽  
Response Surface Methodology ◽  
Polyethylene Glycol ◽  
Response Surface ◽  
Polynomial Equation ◽  
Weight Percent ◽  
Phase System ◽  
Two Phase ◽  
Aqueous Biphasic ◽  
Partitioning Behavior

Abstract Response surface methodology in the framework of central composite design has successfully applied to polyethylene glycol (PEG)-based aqueous two-phase system in order to evaluate its efficiency in extracting Fe from iron ores with respect to PEG molecular weight, PEG concentration and salt concentration factors. Furthermore, ANOVA and multiple regression analysis have provided a second-order polynomial equation that is highly capable of predicting the experimental results. The PEG molecular weight and weight percent of the salt in the feed had a major and minor effects on the iron ion partition coefficient, respectively.

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