Small-angle X-ray scattering and linear melt rheologyof poly(tert-butyl acrylate-g-styrene) graft copolymers

Abstract

The morphology and rheological properties have been studied for poly(tert-butyl acrylate-g-styrene), PtBA-g-S, graft copolymers through the analysis of different samples that varied in the number of grafted repeat units. Small-angle X-ray scattering (SAXS) measurements confirmed phase separation in these samples, and showed the presence of disordered microdomains on those copolymers with a grafting number higher than 7. SAXS results have also shown a significant improvement of microdomain segregation with temperature manifesting considerable changes in both intensity, position and full-width half-maximum of the peak q*, which is attributed to the graft-like nature of these systems. The frequency dependence of the dynamic moduli revealed three relaxation mechanisms. The low-frequency (long time) relaxation was identified with the movement of the whole molecule, the relaxation at intermediate time is related to movement of the grafts, and the high-frequency relaxation is like that found in the transition zone of main chain of poly(tert-butyl acrylate), PtBA. The rheological measurements indicated that the introduction of a small amount of polystyrene, PS, grafts in the PtBA backbone is sufficient to modify mechanical behaviour at low frequencies. Comparison of the rheological properties of the graft copolymers with higher PS content showed that the observed changes in the viscoelastic behaviour under shear seems to be related to both the microphase separated microstructure and the number of grafts present in the copolymers.

Nanostructure and Linear Rheological Response of Comb-like Copolymer PSVS-g-PE Melts: Influences of Branching Densities and Branching Chain Length

“…16,17 The crossover point of G′ and G″ at low frequencies cannot be detected in the master curves of these graft copolymers, resulting from the microphase-separated structure of the samples.…”

Long-Chain Hyperbranched Comb Block Copolymers: Synthesis, Microstructure, Rheology, and Thermal Behavior

“…Indeed, what is surprising is that the rest of the samples obey this principle, given their heterogeneous microstructure. The reason for this is not well understood; however, this behavior has been recently reported in other copolymers with comb block architecture. ,, …”

“…A similar rheological response was observed by De la Fuente and co-workers in poly(tert-butyl acrylate-gstyrene) (PtBA-g-S) and poly(acrylic acid-g-styrene) (P(AA-g-S)) graft copolymers. 21,22 Interestingly, the PSVS-g-PE samples with high branching density, studied by Lin et al, 25 presented homogeneous phase structure at high temperature and rheological behavior similar to linear or comb-like homopolymers. 31−33 Note that the viscoelastic response of the P(AA-g-S) copolymers studied by De la Fuente et al 21 is strongly influenced by the presence of hydrogen bonds between the carboxylic acid groups that lead to an increase of backbone interactions.…”

“…Of particular interest for us are the poly­(A- cb -B) comb blocks (also known as PA- g -PB graft copolymers). Recent studies have shown effective use of comb block (CB) copolymers as compatibilizers of immiscible blends of A and B homopolymers − and as rheology enhancers in blends with A homopolymers and in A/B immiscible blends. , However, only a few studies on the viscoelastic response of CB copolymers have been reported to date. − Stadler et al reported creep and dynamic mechanical measurements of CB copolymers having polyethylene (PE) backbone and ethylene–propylene (EP) side chains (poly­(PE- cb -EP)) . They observed that the molecular weight–viscosity relation in these CB copolymers deviates significantly from the corresponding relations for linear and conventional long-chain branched (LCB) PEs.…”

Improving the hydrophobic, water barrier and crystallization properties of poly(ethylene terephthalate) by incorporating monodisperse SiO2 particles

“…These particles were well dispersed and formed nucleation centers in a polyester matrix which obviously created good surface, thermal and crystallization properties. Also, related to the rule of ‘like dissolves like’, the chain similarity improved the polyester compatibility and mechanical properties 13. Polystyrene (PS) molecular chains ofCH 2 CH 2 phenyl–are similar to PET chains ofCH 2 CH 2 OOCphenylCOO.…”