Microphase Separation in Model 3-MiktoarmStar Copolymers (Simple Graft and Terpolymers). 1. Statics and Kinetics

Abstract

The static and kinetic aspects of the order-disorder transition (ODT) in newly synthesized model 3-miktoarm star copolymer (simple graft) of SI2 type, (polystyrenexpolyisoprenek, and a 3-miktoarm star terpolymer of SIB type, (polystyrene)fpolyisoprene)(polybutadiene), have been studied using smallangle X-ray scattering (SAXS) and rheology. The morphology and the order-disorder transition temperature (TODT) have been identified from the two-dimensional SAXS patterns with shear-oriented samples. Hexagonally ordered cylindrical microdomains aligned along the direction of shear and with TODT = 379 K have been formed for both samples studied. The SAXS profiles at temperatures well above the Tom have been fitted to the mean-field theory (MFT) for graft copolymers. Near the ODT deviations from the theory have been observed and the SAXS data provide unambiguous evidence for the existence of fluctuations. The Tom obtained from rheology is in excellent agreement with the one from SAXS.Discontinuities in the SAXS peak intensity and m the storage modulus near the Tom are more pronounced in these systems as compared to linear diblwks. The ordering kinetics have been studied with rheology and complementary with SAXS. The width of the kinetically accessible metastable region is enlarged as compared to linear diblocks. For shallow quenthes the ordering proceeds by heterogeneous nucleation and growth of three-dimensional grains with cylindrical microstructure. Our kinetic studies probe the metastable states near but below the Tom.

Block Copolymers in External Fields: Rheology, Flow‐Induced Phenomena, and Applications

“…The key findings are qualitatively similar to those reported above [92][93][94]. The observed quantitative differences are attributed to the architecture and often rationalized theoretically [90,95,96]. Along the same lines, linear mixtures of block copolymers with linear homopolymers or other copolymers [71,[97][98][99][100][101] or block copolymers with lengths of different flexibility and or tendency to crystallize [28] have been investigated and continue to pose interesting scientific challenges.…”

Self-assembled block copolymers: Bulk to thin film

“…17 There exist numerous experimental methods to determine the T ODT of block copolymers, which are summarized in Table I. [146][147][148][149][150][151] Among them, small angle X-ray and neutron scatterings (SAXS and SANS) method 99-107 and rheological method [108][109][110][111][112][113][114][115][116][117][118][119][120][121][122][123][124][125] have been widely used. The scattering method could decide the exact microdomain structure but a relatively expensive and huge facilities providing X-ray (or neutron) source should be used to measure the scattering Ñ Ñ Absorbance vs Temperature intensity (I(q)).…”

Viscoelastic Properties of Block Copolymers

“…Because of the distinctly different viscoelastic contrast of the ordered and disordered states, low-frequency rheology is very sensitive for detecting the dissolution of ordered microstructures (Bates 1990, Rosedale 1990, Floudas 1994, Han 1995. Isochronal measurements of the storage modulus performed at low frequencies with low strain amplitudes by slowly heating the specimen provide a good way of locating the T ODT .…”

“…16.1 is depicted by the lines in the figure. The ''fast'' Debye-like process (b ¼ 1) can be attributed to the domain reorientation towards the shear direction and the ''slow'' process to the perfection of the oriented morphology (Floudas 1994). Subsequently, scattering experiments can be used for the identification of the morphology.…”