Composition Fluctuation Inhomogeneity of Symmetric Diblock Copolymers: χ<i><i>N</i></i> Effects at Order-to-Disorder Transition

Jun, Taesuk; Lee, Yonghoon; Jo, Seongjun; Ryu, Chang Y.; Ryu, Du Yeol

doi:10.1021/acs.macromol.7b01946

Cited by 9 publications

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“…The extent of microphase separation present in each of these polymers was analyzed by calculating the Porod scattering invariant from room-temperature SAXS patterns acquired for the quenched samples prior to etching (Figure S16). , Generally, the scattering invariant, Q *, was observed to decrease with decreasing χ N (XS), consistent with weak microphase separation and more homogeneously mixed domains for these diblocks (Figure S16). , On the other hand, diblocks with higher χ N (larger XS) gave larger values of Q *, consistent with microphase segregation even at temperatures slightly above T ODT due to the presence of composition fluctuations. , …”

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confidence: 52%

“… , Generally, the scattering invariant, Q *, was observed to decrease with decreasing χ N (XS), consistent with weak microphase separation and more homogeneously mixed domains for these diblocks (Figure S16). , On the other hand, diblocks with higher χ N (larger XS) gave larger values of Q *, consistent with microphase segregation even at temperatures slightly above T ODT due to the presence of composition fluctuations. , …”

supporting

confidence: 52%

“…13,32 On the other hand, diblocks with higher χN (larger XS) gave larger values of Q*, consistent with microphase segregation even at temperatures slightly above T ODT due to the presence of composition fluctuations. 11,13 Additionally, the SAXS patterns for the unetched samples were fit to the Teubner−Strey (TS) model. 33 Although the TS model was rigorously derived for ternary mixtures of topologically similar bicontinuous microemulsions, we used it as a metric to analyze the domain structure in the limit of zero homopolymer and obtained fits that were in general agreement with the experimental data (Figures S17 and S18).…”

mentioning

confidence: 54%

“…However, numerous experimental − and theoretical studies , have shown that composition fluctuations exist just above T ODT , resulting in a system that remains locally microphase segregated despite a lack of long-range spatial correlations. Indeed, it has been shown that there is a significant change in the interfacial Gaussian curvature yet little change in the domain purity or interfacial area across T ODT , resulting in a dynamic pattern that resembles the late stages of spinodal decomposition. ,− …”

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confidence: 99%

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Molecular Engineering of Nanostructures in Disordered Block Polymers

Hampu

2020

ACS Macro Lett.

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A series of symmetric poly(methyl methacrylate-stat-styrene)-block-polylactide (P(MMA-s-S)-b-PLA) diblock terpolymers with nearly constant molar masses yet varying block interaction parameters were synthesized as a model system to probe the extent and utility of composition fluctuations in the disordered state. A combination of differential scanning calorimetry, dynamic mechanical analysis, and small-angle X-ray scattering revealed that a broad range of segregation strengths ranging from what we ascribe to essentially a mean-field disordered to a fluctuating disordered to an ordered system could be readily obtained by tuning the molar fraction of styrene in these diblocks. The P(MMA-s-S)-b-PLA diblocks were annealed above their order–disorder transition temperatures (T ODT) and rapidly quenched to low temperatures to trap the disordered state via vitrification, as confirmed by scanning electron microscopy. Small-angle X-ray scattering and N2 sorption analysis post-removal of PLA demonstrated that a transition from a very weakly structured, mean-field-like melt to a bicontinuous fluctuating disordered state occurred with increasing segregation strength. This work demonstrates that the extent of microphase segregation as well as the domain continuity of the disordered block polymer melt can be tuned using both synthetic design and thermal stimuli, guiding the design of disordered block polymers with targeted nanostructures that have potential technological utility.

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Molecular Engineering of Nanostructures in Disordered Block Polymers

Hampu

2020

ACS Macro Lett.

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“…The merits of this method are that the experimental T ODT can be measured accurately, and it has a strong dependence on χ, but the method suffers from the fact that the mean-field prediction is seriously inaccurate, particularly for short molecules. To improve the accuracy, a few studies , have fit the ODTs to the Fredrickson–Helfand prediction, (χ N ) ODT = 10.495 + 41.0 N̅ –1/3 , and for even better accuracy, some studies ,, are now fitting to eq . However, this still assumes that the diblock polymers are monodisperse and perfectly symmetric.…”

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Simple and Accurate Calibration of the Flory–Huggins Interaction Parameter

2020

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This paper improves upon a standard method of determining the Flory–Huggins χ parameter, whereby experimental order–disorder transitions (ODTs) of symmetric diblock polymer melts are fit to the mean-field prediction, (χN)ODT = 10.495. The improvement is achieved by switching to an accurate prediction of (χN)ODT from Glaser et al. (Phys. Rev. Lett. 2014, 113, 068302), supplemented with corrections for the small degrees of polydispersity and compositional asymmetry that inevitably exist in real diblock polymers. The first correction is evaluated by simulating polydisperse diblocks over a wide range of invariant polymerization indices, and the second correction is extracted from analogous simulations for compositionally asymmetric diblocks by Ghasimakbari and Morse (Macromolecules 2020, 53, 7399). The resulting calibration method is then demonstrated on 19 different chemical pairs, using previously published experimental data. It provides a considerable increase in accuracy, but yet is nearly as simple to apply as the original version.

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Effect of Molecular Architecture on the Self-Assembly of Bottlebrush Copolymers

Gadelrab

Alexander‐Katz

2020

J. Phys. Chem. B

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The characteristics of a new architecture of bottlebrush copolymers (BBCPs) selfassembly were studied using self-consistent field theory. In this molecule, a series of AB linear diblock side chains were connected at the diblock junction using a C backbone. The control over the linker length and its chemical nature created an additional constraint on the intrinsic AB diblock microphase separation. Increasing side-chain crowding by increasing the grafting density and total degree of polymerization induced improved phase separation. This was reflected in the overall reduction in the effective interaction parameter between the diblocks as well as the abrupt increase in phase density when crossing the order−disorder transition. Side-chain crowding resulted in an increase in the equilibrium domain spacing compared to a linear diblock. On the other hand, the localization of block C at the AB interface generated a diffuse domain boundary and reduction in side-chain stretching. The unique behavior of BBCPs was observed in 1D confined systems where the molecule showed the natural tendency to orient domains parallel to neutral confinement in contrast to the behavior of confined diblocks. Such behavior largely depended on the degree of incompatibility between the AB blocks and BBCP structure. A ternary phase diagram was constructed for different proportions of each block. Rich morphologies of core−shell domains and tiling patterns were observed including octagonal and pentagonal polygons. The unique architecture of this bottlebrush molecule and its improved nanoscale properties make it an attractive candidate for various applications of nanotechnology.

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Composition Fluctuation Inhomogeneity of Symmetric Diblock Copolymers: χN Effects at Order-to-Disorder Transition

Cited by 9 publications

References 45 publications

Molecular Engineering of Nanostructures in Disordered Block Polymers

Molecular Engineering of Nanostructures in Disordered Block Polymers

Simple and Accurate Calibration of the Flory–Huggins Interaction Parameter

Effect of Molecular Architecture on the Self-Assembly of Bottlebrush Copolymers

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