Using surface-induced ordering to probe the isotropic-to-nematic transition for semiflexible polymers

Zhang, Wenlin; Gomez, Enrique D.; Milner, Scott T.

doi:10.1039/c6sm01258b

Cited by 15 publications

(11 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Given that we use a finite set of equally spaced μ values, with spacing δμ, we approximate μt as the middle point between the largest value μ+ that gives S(μ+)≈0, and the smallest value μ− with S(μ−)≠0, i.e., μt=(μ−+μ+)/2±δμ/2. Our simulations suggest a first order phase transition, and this agrees with the corresponding transition in small molecule liquid crystals, but more importantly, this also agrees with simulation results for semi-flexible polymers using a microscopic, Lennard-Jones-type model and mean-field predictions [41,42].…”

Section: Resultssupporting

confidence: 87%

Demixing by a Nematic Mean Field: Coarse-Grained Simulations of Liquid Crystalline Polymers

et al. 2017

View full text Add to dashboard Cite

Liquid crystalline polymers exhibit a particular richness of behaviors that stems from their rigidity and their macromolecular nature. On the one hand, the orientational interaction between liquid-crystalline motifs promotes their alignment, thereby leading to the emergence of nematic phases. On the other hand, the large number of configurations associated with polymer chains favors formation of isotropic phases, with chain stiffness becoming the factor that tips the balance. In this work, a soft coarse-grained model is introduced to explore the interplay of chain stiffness, molecular weight and orientational coupling, and their role on the isotropic-nematic transition in homopolymer melts. We also study the structure of polymer mixtures composed of stiff and flexible polymeric molecules. We consider the effects of blend composition, persistence length, molecular weight and orientational coupling strength on the melt structure at the nano-and mesoscopic levels. Conditions are found where the systems separate into two phases, one isotropic and the other nematic. We confirm the existence of non-equilibrium states that exhibit sought-after percolating nematic domains, which are of interest for applications in organic photovoltaic and electronic devices.

show abstract

Section: Resultssupporting

confidence: 87%

Demixing by a Nematic Mean Field: Coarse-Grained Simulations of Liquid Crystalline Polymers

et al. 2017

View full text Add to dashboard Cite

show abstract

“…For example, semiflexible chains with sufficiently strong nematic interactions will align parallel to a surface, with orientational effects that persist to roughly a radius of gyration from the wall. 44,45 While excluded volume effects become extremely important for stiff chains in solution or confined into two dimensions, 45−50 here polypeptoids are studied in the bulk and in net extend perpendicular to the interface. Further, due to the coupling from each block sharing the same interfacial area, the distance between chains varies as each block is stretched.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Impact of Helical Chain Shape in Sequence-Defined Polymers on Polypeptoid Block Copolymer Self-Assembly

et al. 2018

View full text Add to dashboard Cite

Controlling the self-assembly of block copolymers with variable chain shape and stiffness is important for driving the self-assembly of functional materials containing nonideal chains as well as for developing materials with new mesostructures and unique thermodynamic interactions. The polymer helix is a particularly important functional motif. In the helical chain, the traditional scaling relationships between local chain stiffness and space-filling properties are not applicable; this in turn impacts the scaling relationships critical for governing self-assembly. Polypeptoids, a class of sequence-defined peptidomimetic polymers with controlled helical secondary structure, were used to systematically investigate the impact of helical chain shape on block copolymer self-assembly in a series of poly(n-butyl acrylate)-b-polypeptoid block copolymers. Small-angle X-ray scattering (SAXS) of the bulk materials shows that block copolymers form hexagonally packed cylinder domains. By leveraging sequence control, the polypeptoid block was controlled to form a helix only at the part either adjacent to or distant from the block junction. Differences in domain size from SAXS reveal that chain stretching of the helix near the block junction is disfavored, while helical segments at the center of cylindrical domains contribute to unfavorable packing interactions, increasing domain size. Finally, temperature-dependent SAXS shows that helix-containing diblock copolymers disorder at lower temperatures than the equivalent unstructured diblock copolymers; we attribute this to the smaller effective N of the helical structure resulting in a larger entropic gain upon disordering. These results emphasize how current descriptions of rod/coil interactions and conformational asymmetry for coil polymers do not adequately address the behavior of chain secondary structures, where the scalings of space-filling and stiff−elastic properties relative to chain stiffness deviate from those of typical coil, semiflexible, and rodlike polymers.

show abstract

“…However, the reptative inter-diffusion may not be sufficient to impose strong alignment to polymers at the monomer or the Kuhn segment level, which is critical to accelerating crystal nucleation [20][21][22]. Nevertheless, highly incompatible semiflexible polymers tend to align parallel to interfaces, creating alignment layers of a thickness about a Kuhn length [23][24][25]. The interface-induced alignment may help polymer segments nucleate crystalline order.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulations of Crystal Nucleation near Interfaces in Incompatible Polymer Blends

Zhang

Zou

2021

Polymers

Self Cite

View full text Add to dashboard Cite

We apply molecular dynamics (MD) simulations to investigate crystal nucleation in incompatible polymer blends under deep supercooling conditions. Simulations of isothermal nucleation are performed for phase-separated blends with different degrees of incompatibility. In weakly segregated blends, slow and incompatible chains in crystallizable polymer domains can significantly hinder the crystal nucleation and growth. When a crystallizable polymer is blended with a more mobile species in interfacial regions, enhanced molecular mobility leads to the fast growth of crystalline order. However, the incubation time remains the same as that in pure samples. By inducing anisotropic alignment near the interfaces of strongly segregated blends, phase separation also promotes crystalline order to grow near interfaces between different polymer domains.

show abstract

Using surface-induced ordering to probe the isotropic-to-nematic transition for semiflexible polymers

Cited by 15 publications

References 27 publications

Demixing by a Nematic Mean Field: Coarse-Grained Simulations of Liquid Crystalline Polymers

Demixing by a Nematic Mean Field: Coarse-Grained Simulations of Liquid Crystalline Polymers

Impact of Helical Chain Shape in Sequence-Defined Polymers on Polypeptoid Block Copolymer Self-Assembly

Molecular Dynamics Simulations of Crystal Nucleation near Interfaces in Incompatible Polymer Blends

Contact Info

Product

Resources

About