Phase Behavior of a Weakly Interacting Polystyrene and Poly(n‐hexyl methacrylate) System: Evidence for the Coexistence of UCST and LCST

Abstract

The phase behavior of a weakly interacting binary system composed of deuterated polystyrene (dPS) and poly(n-hexyl methacrylate) (PnHMA) was investigated by the turbidity measurement for the binary blend, and by small angle X-ray scattering (SAXS) and depolarized light scattering for the block copolymers. For the binary dPS/PnHMA blend, a new phase diagram involving both the upper critical solution transition (UCST) and lower critical solution transition (LCST) was observed by the delicate control of molecular weights between dPS and PnHMA. Whereas for the block copolymers such as dPS-block-PnHMA and PS-block-PnHMA, an order-to-disorder transition (ODT) on heating was observed within the experimental temperature range depending on the molecular weight. This coexistence of both a UCST and LCST in the dPS/PnHMA blend consequently represents the experimental evidence that the corresponding (d)PS-b-PnHMAs possess not only ODT, but also lower disorder-to-order transition (LDOT) character driven by a compressibility difference, although the latter is hindered by thermal degradation.

Progression of Alignment in Thin Films of Cylinder-Forming Block Copolymers upon Shearing

“…Since the polymers all appear to approach ψ 2 = 1 at high stress, we set D = 1. In addition, because none of the polymers studied possess a thermally accessible T ODT (the materials degrade before T ODT can be reached), we estimated the T ODT for each diblock using the available literature (see the Supporting Information for details; estimated values of the segregation strength χ N at 150 °C range from 28 to 98 across the series); because the Flory–Huggins interaction parameter for PS–PHMA is known to be very weakly dependent on temperature, , all the estimated T ODT values are quite high (>400 °C), in the regime where the model prediction is insensitive to the value of T ODT ( T ODT ≫ T ). The best-fit parameters for the four polymers as functions of w PS are shown in Figure .…”

“…h i b i t e d .details; estimated values of the segregation strength χN at 150 °C range from 28 to 98 across the series); because the Flory− Huggins interaction parameter for PS−PHMA is known to be very weakly dependent on temperature,63,64 all the estimated T ODT values are quite high (>400 °C), in the regime where the model prediction is insensitive to the value of T ODT (T ODT ≫ T). The best-fit parameters for the four polymers as functions of w PS are shown in Figure3.…”

Synthesis and solution properties of a temperature-responsive PNIPAM–b-PDMS–b-PNIPAM triblock copolymer

“…SAXS/SANS studies have been published on a variety of block copolymers such as the diblock copolymer poly(methoxy diethylene glycol acrylate)-block-polystyrene (PS), 5 the diblock copolymer PS-PNIPAM 6 , deuterated polystyrene and poly(n-hexyl methacrylate) (PnHMA), 7 poly(2-isopropyl-2-oxazoline)-b-poly(2-ethyl-2-oxazoline), 8 C18EO100 9 , polyethylene oxide -poly(2-vinylpyridine) 10 , polyethylene oxide -PNIPAM, 11,12 and PNIPAMpoly(n-butyl acrylate) 13,14 and on triblock copolymers such as (LCP, poly(4-cyanobiphenyl-4-oxyundecylacrylate)) 'A' endblock and a deuterated polystyrene 'B' midblock, 15 PS-PMDEGA-PS, 16,17 and PS-PNIPAM-PS 18 . The most studied class of temperature-responsive polymers are poly(ethylene oxide-block-propylene oxide-blockethylene oxide) PEO-PPO-PEO triblock copolymers known as Pluronics ® .…”

“…The most studied class of temperature-responsive polymers are poly(ethylene oxide-block-propylene oxide-blockethylene oxide) PEO-PPO-PEO triblock copolymers known as Pluronics ® . 7 Detailed SAXS/SANS studies of nanoparticle structures formed in aqueous solution have been published for a variety of commercially available Pluronics ® 19 such as L44, 20 L64, 21 F127, 22,23,24 P84, 25 P85, 26,27 P104, 20 L62, 28 L64, 29 L81, 16 F68, 30 F87, 16 and F88. 16 In our previous work, the internal structure of PNIPAM-b-PEG-b-PNIPAM nanoparticles formed in aqueous solutions was inspected by SANS upon increasing temperature.…”

Various Phase Behaviors of Weakly Interacting Binary Block Copolymer Blends

“…16,32 However, it was reported that the binary blend of polystyrene/poly(nhexyl methacrylate) displays a combined UCST and LCST type at ambient conditions, while the corresponding BCP undergoes a single ODT transition on heating, as shown in Figure 1. 33 Considering that the phase behavior of a binary blend is identical to that of BCP by the differences in the molecular weights, there might have been a missing point on understanding the phase behavior type for the PS-b-PnHMA especially at higher temperature than thermal degradation.…”