Rubber-Modified Polymers. Location of Block Copolymers in Two-Phase Materials

1975 ◽  
pp. 243-256 ◽  
Author(s):  
G. RIESS ◽  
Y. JOLIVET
Keyword(s):  
Block Copolymers ◽  
Two Phase ◽  
Modified Polymers

Phase Behavior in Aqueous Two-Phase Systems Containing Micelle-Forming Block Copolymers

1995 ◽  
Vol 28 (10) ◽  
pp. 3597-3603 ◽  
Author(s):  
Maarten Svensson ◽  
Per Linse ◽  
Folke Tjerneld
Keyword(s):  
Block Copolymers ◽  
Phase Behavior ◽  
Two Phase ◽  
Aqueous Two Phase Systems ◽  
Phase Systems

Properties of Random and Block Copolymers of Butadiene and Styrene. III. Three Sequence Styrene-Butadiene-Styrene Block Polymers

1967 ◽  
Vol 40 (4) ◽  
pp. 1183-1199 ◽  
Author(s):  
C. W. Childers ◽  
G. Kraus
Keyword(s):  
Tensile Strength ◽  
Block Copolymers ◽  
Polymer Chains ◽  
Two Phase ◽  
Styrene Copolymers ◽  
Relaxation Measurements ◽  
Styrene Butadiene Styrene ◽  
Increasing Temperature ◽  
Styrene Butadiene ◽  
Butadiene Styrene

Abstract In butadiene styrene copolymers containing long block sequences chain segments associate with like segments to form a two phase structure. Properties of such polymers are dependent not only on composition and molecular weight but also on block sequence along the chain. Polymers containing two or more polystyrene blocks per molecule form networks and exhibit elastomeric properties in the uncured state resembling those of filler reinforced vulcanizates. This behavior is shown both by linear styrene-butadiene-styrene elastomers and multichain block copolymers branched in the polybutadiene blocks. A prominent loss tangent peak was observed around —40° C for the multichain polymers. Stress strain following prestretching and stress relaxation measurements indicate some shifting of polystyrene associations during stretching. Tensile strength is reduced by increasing temperature and addition of plasticizers. Reinforcement by polystyrene domains in vulcanized block copolymers is evident from tensile strength, dynamic modulus, and swelling measurements, but decreases with increased crosslinking. The number of styrene sequences in the primary molecules is less important after vulcanization as crosslinking destroys the individuality of the original polymer chains.

Effect of Temperature on Stress-Optical Properties of Styrene Butadiene Block Copolymers

1967 ◽  
Vol 40 (5) ◽  
pp. 1373-1380 ◽  
Author(s):  
E. Fischer ◽  
J. F. Henderson
Keyword(s):  
Optical Properties ◽  
Block Copolymers ◽  
Network Structure ◽  
Effect Of Temperature ◽  
Stress Strain ◽  
Two Phase ◽  
Phase Systems ◽  
Effective Network ◽  
Restricted Mobility ◽  
Styrene Butadiene

Abstract Stress, strain, and optical properties of three elastomeric styrene butadiene block copolymers containing 31, 40 and 49 wt per cent styrene were studied as a function of temperature. Mechanical and optical properties indicate that these materials are two phase systems in which the polybutadiene chains form an elastomeric phase and the polystyrene a glassy phase with the latter providing physical crosslinks. Birefringence measurements indicate that decreases in modulus and strength of these materials are associated with decrease in concentration of elastically effective network chains. Independence of stress-optical coefficient of temperature suggests that the decrease in concentration of elastically effective chains is not due to onset of rubberlike behavior or flow within the polystyrene regions themselves, at least for temperatures below about 70° C. Rather, the decrease seems to be associated with increased mobility of the polybutadiene chains at higher temperatures, which also leads to an increase in the rate of stress relaxation. Birefringence measured during extension and retraction showed that stress strain hysteresis is due to restricted mobility of polybutadiene chain segments rather than to permanent viscous flow or to change in the effective network structure of the block copolymers. The ultimate properties of these rubbers were well correlated with the effective network structure in undeformed specimens.

scholarly journals Organosilica-Modified Multiblock Copolymers for Membrane Gas Separation

Polymers ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 3579
Author(s):  
Ilsia M. Davletbaeva ◽  
Alexander Yu. Alentiev ◽  
Zulfiya Z. Faizulina ◽  
Ilnaz I. Zaripov ◽  
Roman Yu. Nikiforov ◽  
...  
Keyword(s):  
Block Copolymers ◽  
Toluene Diisocyanate ◽  
Multiblock Copolymers ◽  
Gas Solubility ◽  
Membrane Gas Separation ◽  
Modified Polymers ◽  
Temperature Relaxation ◽  
Solubility Coefficients ◽  
Modified Block ◽  
The Ideal

Organosubstituted silica derivatives were synthesized and investigated as modifiers of block copolymers based on macroinitiator and 2,4-toluene diisocyanate. A peculiarity of the modified block copolymers is the existence in their structure of coplanar rigid polyisocyanate blocks of acetal nature (O-polyisocyanates). Organosubstituted silica derivatives have a non-additive effect on high-temperature relaxation and α-transitions of modified polymers and exhibit the ability to influence the supramolecular structure of block copolymers. The use of the developed modifiers leads to a change in the gas transport properties of block copolymers. The increase of the permeability coefficients is due to the increase of the diffusion coefficients. At the same time, the gas solubility coefficients do not change. An increase in the ideal selectivity for a number of gas pairs is observed. An increase in the selectivity for the CO2/N2 gas pair (from 25 to 39) by 1.5 times demonstrates the promising use of this material for flue gases separation.

Aqueous two-phase systems containing self-associating block copolymers

1999 ◽  
Vol 839 (1-2) ◽  
pp. 71-83 ◽  
Author(s):  
Mårten Svensson ◽  
Kristina Berggren ◽  
Andres Veide ◽  
Folke Tjerneld
Keyword(s):  
Block Copolymers ◽  
Two Phase ◽  
Aqueous Two Phase Systems ◽  
Phase Systems

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 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.

Phase Transitions in Polyester-Polyether Copolymers

2020 ◽  
Vol 869 ◽  
pp. 308-314
Author(s):  
Arsen M. Kharaev ◽  
Rima Ch. Bazheva ◽  
Zakhirat Kh. Sultigova ◽  
Zareta I. Inarkieva ◽  
Asker Kongapshev
Keyword(s):  
Differential Scanning Calorimetry ◽  
Phase Transitions ◽  
Block Copolymers ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
Polytetramethylene Oxide

Using differential scanning calorimetry, phase transitions in polycarbonate-polytetramethylene oxide block copolymers were studied. It is shown that, depending on the ratio of rigid polycarbonate and flexible polytetramethylene oxide units, block copolymers can be two-phase or four-phase. It is shown that phase transitions in copolymers of a polyester-polyether depend on the ability to crystallize the components.

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