Comparison of Interfacial Width of Block Copolymers of d₈-Poly(methyl methacrylate) with Various Poly(n-alkyl methacrylate)s and the Respective Homopolymer Pairs as Measured by Neutron Reflection

Abstract

The compatibility of d8-poly(methyl methacrylate) (d8-PMMA) and a series of poly(n-alkyl methacrylate)s (PnAlkMA) is studied by systematic variation of the length of the n-alkyl group from ethyl (EMA) to n-pentyl (nPenMA). Simultaneously, a series of symmetric diblock copolymers comprised of d8-PMMA and of PnAlkMA ranging from ethyl to n-hexyl (nHMA) is synthesized. Small-angle X-ray data of bulk samples of d8-PMMA-b-PEMA show that this block copolymer is in the disordered state. A change in the χ over 1/T plot occurs between 120 and 130 °C owing to fluctuations. All other block copolymers are in the ordered state at any temperature. The neutron reflection data of d8-PMMA-b-PEMA show a damped cosine concentration depth profile characteristic for thin films of block copolymers in the disordered state. In contrast, the bilayer film of the respective homopolymer pair indicates immiscibility. Neutron reflection measurements on thin films of diblock copolymers ranging from d8-PMMA-b-PnPrMA to d8-PMMA-b-PnHMA and of bilayer films of d8-PMMA and the respective PnAlkMAs show a decreasing apparent interfacial width with increasing length of the n-alkyl group. Taking into account the contributions of capillary waves leads to the inherent interfacial width. By use of the theoretical approach of Matsen and Bates, it is possible to extract the Flory-Huggins χ-parameter between the blocks and the average segment length.

Correlation between Phase Behavior and Tensile Properties of Diblock Copolymers

“…For a symmetrical dPMMA-b-PBMA diblock copolymer with 45.7 kg/mol, the interaction parameter was determined to PMMA/PBMA ) 0.062 at T ) 140°C. 33 In contrast, for dPS-b-PBMA diblock copolymers was determined to 0.0133 at T ) 140°C by SANS, which is smaller compared to that of PMMA-b-PBMA diblock copolymers. However, for both systems is much smaller than obtained for poly(styrene-b-isoprene) diblock copolymers ( ) 71.4/T -0.00857 37 ).…”

Estimating the segregation strength of microphase‐separated diblock copolymers from the interfacial width

“…Thin film measurements of the interfacial width of PBMA–PMMA, PS–PMMA, and PS‐ b ‐poly(2‐vinylpyridine) (PS–P2VP), made by NR, and PS‐ b ‐1,4‐polyisoprene (PS–PI), made by X‐ray reflectivity (XRR), are also included, as is a measurement of the interfacial width of a PS–PMMA thin film by soft X‐ray scattering (SoXS, which is functionally equivalent to the SAXS measurements reported herein) . All of the thin film measurements were reported at room temperature (below the glass transition temperature of at least one of the blocks) following extensive annealing in the melt and quenching to room temperature.…”

“…Few attempts have been made to measure χ N from diblocks in the ordered state . Prior work made use of theoretical predictions for the domain spacing, d , and the width of the interfacial mixing region, t , in the lamellar phase as a function of χ N ; these predictions were made by SCFT or the earlier strong segregation theory (SST, valid for χ N ≫ (χ N ) ODT ).…”

“…Prior work made use of theoretical predictions for the domain spacing, d , and the width of the interfacial mixing region, t , in the lamellar phase as a function of χ N ; these predictions were made by SCFT or the earlier strong segregation theory (SST, valid for χ N ≫ (χ N ) ODT ). Scherble et al estimated χ for a series of methacrylate‐based diblocks from the interfacial width measured by neutron reflectivity (NR), after applying a correction for the effect of thermocapillary waves. A direct comparison between χ N determined from the interfacial width in the ordered state and χ N determined by one of the aforementioned methods was not available; however, the authors noted that the capillary wave correction produced a large uncertainty in χ (50–100%).…”

Synthesis of high molecular weight poly(styrene-b-methyl methacrylate) using a plug flow reactor system by anionic polymerization

“…Additionally, DPHLi has been used as an initiator for the polymerization of butadiene, styrene, and polar monomers, such as alkyl methacrylates, 2-vinylpyridine. 3,[25][26][27][28][29][30] In this experiment, the homopolymerization of styrene with DPHLi was performed in the PFR system at various reaction conditions (flow rates, concentrations). DPHLi was in the R1 reservoir filled with THF at 0 o C. The purified monomer was added to R2 filled with THF (concentration: 35 Table III.…”