scholarly journals The Micellization of Well-Defined Single Graft Copolymers in Block Copolymer/Homopolymer Blends

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 833
Author(s):  
Eleni Pavlopoulou ◽  
Kiriaki Chrissopoulou ◽  
Stergios Pispas ◽  
Nikos Hadjichristidis ◽  
Spiros H. Anastasiadis
Keyword(s):  
Graft Copolymer ◽  
Diblock Copolymers ◽  
Volume Fraction ◽  
Graft Copolymers ◽  
Critical Length ◽  
Molecular Weights ◽  
X Ray Scattering ◽  
Homopolymer Blends ◽  
Copolymer Micelles ◽  
Macromolecular Architecture

A series of well-defined (polyisoprene)2(polystyrene), I2S, single graft copolymers with similar total molecular weights but different compositions, fPS, were blended with a low molecular weight polyisoprene homopolymer matrix at a constant concentration 2 wt%, and the micellar characteristics were studied by small-angle x-ray scattering. To investigate the effect of macromolecular architecture on the formation and characteristics of micelles, the results on the single graft copolymers were compared with those of the corresponding linear polystyrene-b-polyisoprene diblock copolymers, SI. The comparison reveals that the polystyrene core chains are more stretched in the case of graft copolymer micelles. Stretching turned out to be purely a result of the architecture due to the second polyisoprene block in the corona. The micellization of a (polystyrene)2(polyisoprene), S2I, graft copolymer was also studied, and the comparison with the results of the corresponding I2S and SI copolymers emphasizes the need for a critical core volume rather than a critical length of the core-forming block, in order to have stable micelles. Finally, the absence of micellization in the case of the I2S copolymer with the highest polystyrene volume fraction is discussed. For this sample, macrophase separation occurs, with polyisoprene cylinders formed in the copolymer-rich domains of the phase-separated blends.

Synthesis and characterization of amphiphilic graft copolymers with hydrophobic poly(α-methylstyrene) backbone and hydrophilic poly(n-vinylpyrrolidone) side chains

e-Polymers ◽  
2012 ◽  
Vol 12 (1) ◽  
Author(s):  
Fatima Zohra Sebba ◽  
Seghier Ould Kada ◽  
Mohamed Benaicha ◽  
Nerjesse Nemiche
Keyword(s):  
Graft Copolymer ◽  
Graft Copolymers ◽  
Radical Copolymerization ◽  
Side Chains ◽  
Free Radical Copolymerization ◽  
Good Efficiency ◽  
Molecular Weights ◽  
Grafting Reaction ◽  
Viscosity Variation ◽  
End Capping

AbstractIn this study, 2-oxopropylmethacrylate-terminated poly(N-vinyl-2- pyrrolidone) is produced by cationic polymerization using HClO4 as an initiator. Termination (end capping) step is accomplished using 2- hydroxypropylmethacrylate (2HPMA) and the polymer product has different chain lengths of molecular weight averages ranging from 672 to 3049 g/mol. The study also synthesised amphipathic graft copolymers having hydrophobic poly(α- methylstyrene) as a backbone chain and hydrophilic poly(N-vinyl-2-pyrrolidone) (PVP) as side chains of various lengths. The copolymer synthesis was accomplished by free radical copolymerization of ω-oxopropylmethacrylate PVP in the presence of α-methyl styrene initiated with benzoyl peroxide. Measurements of the dynamic viscosity of the polymer solution (20% weight of macromonomers in ethanol) show that the viscosity is proportional to the average molecular weights M̅n . However, a reverse behaviour of the viscosity variation with regard to M̅n is observed for graft copolymer samples. The viscosity variation with respect to the graft copolymer mass must be due to steric effects, which are strongly pronounced in grafted copolymer chains. Appearance of the number of side chains attached to poly(α-methylstyrene) backbone reveals that the grafting reaction has occurred with good efficiency.

Recent morphological surprises in diblock copolymer systems

1994 ◽  
Vol 52 ◽  
pp. 438-439
Author(s):  
M. M. Disko ◽  
S. K. Behal ◽  
K. S. Liang ◽  
R. J. Roe ◽  
K. J. Jeon
Keyword(s):  
Diblock Copolymer ◽  
Diblock Copolymers ◽  
Volume Fraction ◽  
Thin Sections ◽  
Flexible Control ◽  
Molecular Weights ◽  
Interfacial Surfaces ◽  
Double Diamond ◽  
Selective Separations ◽  
Styrene Butadiene

Diblock copolymers form ordered interfacial surfaces that range from lamellae, to cylinders, to the ordered bicontinuous double diamond (OBDD) structure, and spheres on a cubic lattice as the size of one component is increased. Flexible control of these materials presents an opportunity for structural materials, adhesives and selective separations. Mixtures of diblock copolymers with homopolymers exhibit similar structures due to changes in the interfacial curvature that accompany "swelling" the like-component of the diblock with homopolymer. Ordering behavior in systems of this type depends on the elastic properties and molecular weights (MW's) of the polymers, annealing temperature and annealing time. We have examined the changes in morphology of a styrene-butadiene (SB) diblock copolymer mixed with homopolymer polystyrene (hS). Sample made by casting from toluene solution, annealing at 130°C for 2-10 days, staining B-rich regions with OsO4, and microtoming thin-sections at -90°C. The SB MW was 49 800 g/mol with an S-block MW of 25 500 g/mol, and 24 400 g/mol for the B-block. Two hS components were used, having MW's of 26 000 g/mol (h26) and 19 300 g/mol (h19). We refer to the samples by the hS molecular weight and total polystyrene volume fraction, e.g. h26/0.67.

Liquid crystalline assembly of rod–coil diblock copolymer and homopolymer blends by dissipative particle dynamics simulation

Soft Matter ◽  
2014 ◽  
Vol 10 (33) ◽  
pp. 6278-6285 ◽  
Author(s):  
Huihui Wu ◽  
Linli He ◽  
Xianghong Wang ◽  
Yanwei Wang ◽  
Zhouting Jiang
Keyword(s):  
Diblock Copolymer ◽  
Liquid Crystalline ◽  
Diblock Copolymers ◽  
Volume Fraction ◽  
Dissipative Particle Dynamics ◽  
Particle Dynamics ◽  
Dynamics Simulation ◽  
Homopolymer Blends ◽  
Dissipative Particle Dynamics Simulation

Liquid crystalline assembly of rod–coil diblock copolymers blended with homopolymers is investigated by dissipative particle dynamics simulation, considering systematically the effect of the interactions between rods and coils, volume fraction and length of added coil or rod homopolymers.

Morphological behavior of compatibilized ternary blends prepared by mechanical mixing

1993 ◽  
Vol 51 ◽  
pp. 1200-1201
Author(s):  
S.D. Smith ◽  
R.J. Spontak ◽  
D.H. Melik ◽  
S.M. Buehler ◽  
K.M. Kerr ◽  
...  
Keyword(s):  
Interfacial Adhesion ◽  
Diblock Copolymers ◽  
Ternary Blends ◽  
Mechanical Mixing ◽  
Design Considerations ◽  
Covalently Bonded ◽  
Homopolymer Blends ◽  
Emulsifying Agent ◽  
Surface Active ◽  
Low Entropy

When blended together, homopolymers A and B will normally macrophase-separate into relatively large (≫1 μm) A-rich and B-rich phases, between which exists poor interfacial adhesion, due to a low entropy of mixing. The size scale of phase separation in such a blend can be reduced, and the extent of interfacial A-B contact and entanglement enhanced, via addition of an emulsifying agent such as an AB diblock copolymer. Diblock copolymers consist of a long sequence of A monomers covalently bonded to a long sequence of B monomers. These materials are surface-active and decrease interfacial tension between immiscible phases much in the same way as do small-molecule surfactants. Previous studies have clearly demonstrated the utility of block copolymers in compatibilizing homopolymer blends and enhancing blend properties such as fracture toughness. It is now recognized that optimization of emulsified ternary blends relies upon design considerations such as sufficient block penetration into a macrophase (to avoid block slip) and prevention of a copolymer multilayer at the A-B interface (to avoid intralayer failure).

Preparation of graft copolymers by the reaction of polymeric acyl chlorides with monohydroxy-terminated polymers: An introductory study

1988 ◽  
Vol 53 (8) ◽  
pp. 1735-1744 ◽  
Author(s):  
Jitka Horská ◽  
Jaroslav Stejskal ◽  
Pavel Kratochvíl ◽  
Aubrey D. Jenkins ◽  
Eugenia Tsartolia ◽  
...  
Keyword(s):  
Light Scattering ◽  
Chemical Composition ◽  
Statistical Model ◽  
Graft Copolymers ◽  
Coupling Reaction ◽  
Molecular Characteristics ◽  
Gel Formation ◽  
Acyl Chlorides ◽  
Molecular Weights

An attempt was made to prepare well-defined graft copolymers by the coupling reaction between acyl chloride groups located along the backbone chain and monohydroxy-terminated grafts prepared separately. The molecular weights and the parameters of heterogeneity in chemical composition of the products were determined by light scattering and osmometry. The determination of molecular characteristics revealed that the degree of grafting was low. The results therefore could not be confronted with a statistical model at this stage. The problems encountered in the synthesis, e.g., gel formation, and the data relating to the soluble products are discussed.

Mesoscopic structure of SiC fibers by neutron and x-ray scattering

1996 ◽  
Vol 11 (5) ◽  
pp. 1169-1178 ◽  
Author(s):  
Kentaro Suzuya ◽  
Michihiro Furusaka ◽  
Noboru Watanabe ◽  
Makoto Osawa ◽  
Kiyohito Okamura ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Volume Fraction ◽  
X Rays ◽  
X Ray ◽  
Sic Fibers ◽  
X Ray Scattering ◽  
Mesoscopic Structure ◽  
Angle Scattering ◽  
Momentum Transfer Range ◽  
First Time

Mesoscopic structures of SiC fibers produced from polycarbosilane by different methods were studied by diffraction and small-angle scattering of neutrons and x-rays. Microvoids of a size of 4–10 Å in diameter have been observed for the first time by neutron scattering in a medium momentum transfer range (Q = 0.1–1.0 Å−1). The size and the volume fraction of β–SiC particles were determined for fibers prepared at different heat-treatment temperatures. The results show that wide-angle neutron scattering measurements are especially useful for the study of the mesoscopic structure of multicomponent materials.

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.

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