Mechanical Properties of Blends of Crystallizable Polybutadienes Containing Amorphous Polybutadiene Diblock Copolymers

1994 ◽  
Vol 67 (2) ◽  
pp. 342-347
Author(s):  
Moira Marx Nir ◽  
Robert E. Cohen
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Surface Area ◽  
Diblock Copolymer ◽  
Diblock Copolymers ◽  
Tensile Failure ◽  
Interfacial Surface ◽  
Failure Properties ◽  
Enhanced Properties

Abstract Tensile failure properties of syndiotactic 1,2 polybutadiene/trans 1,4 polybutadiene crystalline blends are improved by addition of 5–10% amorphous 1,2 polybutadiene/1,4 polybutadiene diblock copolymer. The effect of block molecular weight and microphase behavior of the diblock copolymer was investigated. Heterogeneous diblocks enhance blend properties to a greater extent than homogeneous diblocks. In blends with enhanced properties, percent coverage of interfacial surface area by diblock is on the order of 10%.

The Ordered Bicontinuous Double Diamond Structure in Binary Blends of Diblock Copolymer and Homopolymer.

1989 ◽  
Vol 171 ◽  
Author(s):  
Karen I. Winey ◽  
Edwin L. Thomas
Keyword(s):  
Molecular Weight ◽  
Diblock Copolymer ◽  
Diblock Copolymers ◽  
Composition Range ◽  
Volume Fraction ◽  
Diamond Structure ◽  
Binary Blends ◽  
Resultant Effect ◽  
Strong Segregation ◽  
Double Diamond

ABSTRACTWe report the observation of the ordered bicontinuous double diamond (OBDD) structure in binary blends of poly(styrene-isoprene) diblock copolymer and homopolystyrene. The overall polystyrene volume fraction range is 64 - 67 PSvol% for the OBDD structure in binary blends of a lamellar diblock (SI 27/22) and a homopolymer (14.0 hPS). This composition range is approximately within the polystyrene volume fraction range established for pure diblock copolymers in the strong segregation regime having the OBDD structure. Ordered lamellae are observed at approximately 65 PSvol% when the homopolystyrene molecular weight is greater than the molecular weight of the polystyrene block of the copolymer. This observation is discussed in terms of the decreased degree of mixing between the homopolymer and the corresponding block and the resultant effect on the interfacial curvature.

Modification of Interfacial Properties of Polymer Blends with Diblock Copolymer

1996 ◽  
Vol 461 ◽  
Author(s):  
S. Kim ◽  
C. C. Han
Keyword(s):  
Molecular Weight ◽  
Phase Separation ◽  
Polymer Blends ◽  
Diblock Copolymer ◽  
Diblock Copolymers ◽  
Phase Region ◽  
Domain Growth ◽  
Two Phase ◽  
Phase Separation Kinetics ◽  
Styrene Butadiene

ABSTRACTThe effect of diblock copolymer on the phase-separation process of polymer blends has been investigated by using light scattering and optical microscopic observations. To quench the system into the two phase region, a shear-jump technique is employed instead of the conventional temperature-jump technique. The samples studied are blends of low-molecular-weight polystyrene and polybutadiene with and without added styrene-butadiene block copolymer as a compatibilizer. It was observed that the addition of diblock copolymers could accelerate the phase separation kinetics depending on the shear history. As the concentration of diblock copolymer increases, the distribution of domain sizes becomes narrower and the growth rate slows down. The extent of slowing-down depends on the molecular weight and concentration of the copolymer. The time dependence of domain growth is clearly observed with optical microscopy.

Thermo-responsive metallo-supramolecular gels based on terpyridine end-functionalized amphiphilic diblock copolymers

2013 ◽  
Vol 1499 ◽  
Author(s):  
Jérémy Brassinne ◽  
Charles-André Fustin ◽  
Jean-François Gohy
Keyword(s):  
Mechanical Properties ◽  
Diblock Copolymer ◽  
Self Assembly ◽  
Micellar Solution ◽  
Diblock Copolymers ◽  
Solution Temperature ◽  
Selective Solvent ◽  
Critical Solution Temperature ◽  
Terpyridine Ligands ◽  
Amphiphilic Diblock Copolymers

ABSTRACTA thermo-responsive hydrogel was prepared on the basis of terpyridine endfunctionalized polystyrene-block-poly(N-isopropylacrylamide) diblock copolymer. As a first level of assembly, the copolymer was dissolved in a selective solvent to yield micelles bearing terpyridine ligands at the extremity of the coronal chains. The second level of self-assembly was triggered upon addition of metal ions to the micellar solution. Mechanical properties of the accordingly obtained micellar gel were finally characterized by rotational rheometry, below and above the lower critical solution temperature.

Block Copolymer Thin Films Above and Below the Order-Disorder Transition Temperature

2000 ◽  
Vol 629 ◽  
Author(s):  
Ratchana Limary ◽  
Peter F. Green
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Molecular Weight ◽  
Transition Temperature ◽  
Block Copolymer ◽  
Film Thickness ◽  
Diblock Copolymer ◽  
Diblock Copolymers ◽  
Microphase Separation ◽  
Disorder Transition Temperature

ABSTRACTSymmetric diblock copolymers undergo a disorder to order transition below a microphase separation transition temperature. In this temperature range the structure is characterized by alternating lamellae of thickness L. In thin film geometries, the lamellae are oriented normal to the substrate if there is a preferential interaction between either of the block constituents and the substrate/copolymer or copolymer/vacuum interfaces. Depending on the relation between the film thickness and L, the topography of the film might comprise of holes, islands or spinodal-like structures. We show that in a polystyrene-b-poly(methyl methacrylate) diblock copolymer of molecular weight 20, 000 g/mol, above the microphase separation transition temperature, the topography of the film depends on the thickness. A heirarchy of bicontinuous patterns and holes is observed with increasing film thickness for films thinner than 35 nm.

scholarly journals Using Poloxamer® 407 as Building Block of Amphiphilic Poly(ether urethane)s: Effect of its Molecular Weight Distribution on Thermo-Sensitive Hydrogel Performances in the Perspective of Their Biomedical Application

2020 ◽  
Vol 7 ◽  
Author(s):  
Rossella Laurano ◽  
Michela Abrami ◽  
Mario Grassi ◽  
Gianluca Ciardelli ◽  
Monica Boffito ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Ethylene Oxide ◽  
Diblock Copolymer ◽  
Diblock Copolymers ◽  
Average Molecular Weight ◽  
Gelation Time ◽  
Resonance Spectroscopy ◽  
Heterogeneous Structure ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene

Due to its hydroxyl terminal groups, Poloxamer® 407 (P407), a commercially available poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer can be used as macrodiol for the synthesis of high molecular weight amphiphilic poly(ether urethane)s (PEUs). This work was aimed at studying the effect of P407 purification by removing PEO-PPO diblock copolymer by-products on the chemical properties of PEU polymer and the physical properties of PEU hydrogels. Removal of PEO-PPO diblock copolymers (P407_P) was found to preserve the thermo-responsiveness of resulting hydrogels, although slightly lower gelation onset temperature (Tonset) was found for P407_P (15.3°C) vs. P407 (16.7°C) hydrogels (25% w/V) as assessed through temperature ramp test. P407 and P407_P were then reacted with 1,6-diisocyanatohexane and 1,4-cyclohexanedimethanol to synthesize two different PEUs, coded as CHP407 and CHP407_P, respectively. Lower Number Average Molecular Weight (Mn¯) and higher polydispersity Index (D) was measured for CHP407 (Mn¯: 34 kDa, D: 1.6) respect to CHP407_P (Mn¯: 40 kDa, D: 1.4) as a consequence of macrodiol purification. CHP407_P hydrogels formed bigger micelles (43.9 ± 4.1 nm vs. 28.7 ± 4 nm) while showed similar critical micellar temperatures (22.1°C vs. 21.6°C) respect to CHP407 formulations. Sol-to-gel transition of CHP407 and CHP407_P hydrogels was similar while CHP407_P gelation time at 37°C was longer as assessed by tube inverting test. The rheological analysis showed slightly lower Tonset for CHP407_P hydrogels (15% w/V), probably due to larger micelle size, promoting micellar assembly. However, CHP407_P hydrogels showed a significantly lower critical strain than CHP407 hydrogels, as assessed by strain sweep test, suggesting their higher brittleness due to a lower density of intermicellar bridge chains. Nano-scale hydrogel characterization by Low-Field Nuclear Magnetic Resonance spectroscopy supported previous findings, showing lower spin-spin relaxation time (i.e., 1,259 ms) for CHP407_P than for CHP407 hydrogels (i.e., 1,560 ms) at 37°C, which suggested the formation of a more tightly packed network for CHP407_P than CHP407 hydrogel. Finally, lower swelling capability and resistance against dissolution were measured for CHP407_P hydrogels. Overall, the here‐reported results suggested that the heterogeneous structure in the CHP407 hydrogel network caused by the presence of diblock copolymer-based macrodiols improved PEU hydrogel properties in light of their applicability in the biomedical field.

Block Copolymers Poly(2,6-dimethyl-1,4-phenylene oxide)-poly(6-hexanelactam). Preparation and Composition

1993 ◽  
Vol 58 (11) ◽  
pp. 2574-2582 ◽  
Author(s):  
Jaroslav Stehlíček ◽  
Rudolf Puffr
Keyword(s):  
Molecular Weight ◽  
Block Copolymers ◽  
Diblock Copolymer ◽  
Anionic Polymerization ◽  
Diblock Copolymers ◽  
Toluene Solution ◽  
Low Molecular Weight ◽  
Phenylene Oxide ◽  
End Groups ◽  
Tolylene Diisocyanate

Poly(2,6-dimethyl-1,4-phenylene oxide)-poly(6-hexanelactam) diblock copolymers were prepared from low-molecular weight poly(2,6-dimethyl-1,4-phenylene oxide) by transforming its phenolic end groups via the reaction with 2,4-tolylene diisocyanate and 6-hexanelactam to polymeric initiators and the subsequent anionic polymerization of 6-hexanelactam. The polymerization of 6-hexanelactam was carried out in bulk or toluene solution. The content of the 6-hexanelactam homopolymer was estimated by TLC showing that the pure diblock copolymer can be prepared in toluene. The reason for relatively low yields is discussed.

The Synthesis of Polystyrene-B-Poly(4-Vinylpyridine) and its Application

2012 ◽  
Vol 161 ◽  
pp. 157-161
Author(s):  
Si Kai Zhou ◽  
Ya Juan Xu ◽  
Shao Ming Fang
Keyword(s):  
Molecular Weight ◽  
Free Radical ◽  
Molecular Weight Distribution ◽  
Diblock Copolymer ◽  
Weight Distribution ◽  
Diblock Copolymers ◽  
Gel Permeation Chromatography ◽  
Atomic Force ◽  
Gel Permeation ◽  
Living Free Radical Polymerization

a system of polystyrene and polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) were synthesized by using living free radical in the presence of 4-hydroxyl-2, 2, 6, 6-tetramethylpiperridine-oxyl-1(HTEMPO•) and (BPO). The polystyrene and diblock copolymers were characterized by gel permeation chromatography (GPC) and atomic force microscope (AFM). The results suggested that the polymerization of styrene in the presence of 4-hydroxyl-2, 2, 6, 6-tetramethylpiperridine-oxyl-1(HTEMPO•) and benzoyl peroxide (BPO) can be prepared with molecular weight distribution in the range of 1.15 to 1.25. The polystyrene with living groups can continuously initiate the living free radical polymerization of 4-Vinylpyridine to form the polystyrene-block-poly (4-vinylpyridine) with molecular weight distribution in the range of 1.08 to 1.35. The AFM of diblock indicated the diblock copolymer（PS-b-P4VP） is a good compatibilizer for PS and P4VP.

scholarly journals Nanoporous Quasi-High-Entropy Alloy Microspheres

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 345 ◽  
Author(s):  
Lianzan Yang ◽  
Yongyan Li ◽  
Zhifeng Wang ◽  
Weimin Zhao ◽  
Chunling Qin
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
High Specific Surface Area ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Hierarchical Porous

High-entropy alloys (HEAs) present excellent mechanical properties. However, the exploitation of chemical properties of HEAs is far less than that of mechanical properties, which is mainly limited by the low specific surface area of HEAs synthesized by traditional methods. Thus, it is vital to develop new routes to fabricate HEAs with novel three-dimensional structures and a high specific surface area. Herein, we develop a facile approach to fabricate nanoporous noble metal quasi-HEA microspheres by melt-spinning and dealloying. The as-obtained nanoporous Cu30Au23Pt22Pd25 quasi-HEA microspheres present a hierarchical porous structure with a high specific surface area of 69.5 m2/g and a multiphase approximatively componential solid solution characteristic with a broad single-group face-centered cubic XRD pattern, which is different from the traditional single-phase or two-phase solid solution HEAs. To differentiate, these are named quasi-HEAs. The synthetic strategy proposed in this paper opens the door for the synthesis of porous quasi-HEAs related materials, and is expected to promote further applications of quasi-HEAs in various chemical fields.

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