Liquid crystalline block and graft copolymers

Fischer, Hartmut; Poser, S.

doi:10.1002/actp.1996.010471001

Cited by 76 publications

(74 citation statements)

References 87 publications

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“…Similar behavior of enhanced stability of spherical phases has been previously reported with side-chain liquid crystalline diblock copolymers. 40,41 Finally, we would like to point out that the lam-in-HPL structure was repeatedly observed despite careful annealing. At present, we cannot conclusively determine whether it is a very long-lived metastable state or equilibrium structure.…”

Section: Resultsmentioning

confidence: 99%

Self-Assembled Structures in Diblock Copolymers with Hydrogen-Bonded Amphiphilic Plasticizing Compounds

et al. 2006

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Hydrogen-bonding amphiphilic low molecular weight plasticizing compounds to one block of diblock copolymers to form supramolecular comblike blocks leads to hierarchical self-assembly at the block copolymer (long) and amphiphile (short) length scales, in which lamellar-in-lamellar order and the related phase transitions have previously been shown to allow thermal switching of electrical and optical properties [Science 1998, 280, 557; Nat. Mater. 2004, 3, 872]. In this work other hierarchies and phase transitions are systematically searched, a particular interest being hierarchies containing gyroid structures and the related order−order transitions. Polymeric supramolecular comb−coil diblock copolymers consisting of a polystyrene (PS) coillike block and a supramolecular comblike block based on poly(4-vinylpyridine) (P4VP) are used, where the pyridines are either directly hydrogen bonded with 3-pentadecylphenol (PDP), i.e., PS-block-P4VP(PDP)1.0, or first protonated with methanesulfonic acid (MSA) and then hydrogen bonded to PDP, i.e., PS-block-P4VP(MSA)1.0(PDP)1.0. In this way the comblike block can be noncharged or charged. The morphologies were determined using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) at different temperatures. In the case of PS-block-P4VP(PDP)1.0, all classical diblock copolymer morphologies were observed at room temperature, where the P4VP(PDP)1.0 domains contain an additional lamellar structure due to the supramolecular comblike blocks. Here we report novel gyroid and hexagonal perforated layer morphologies, i.e., where the PS and P4VP(PDP)1.0 blocks form gyroid or hexagonal perforated layer order and the P4VP(PDP)1.0 domains have an internal lamellar order. Heating past ca. T = 60 °C causes an order−disorder transition within the P4VP(PDP)1.0 domains. Further heating leads to gradually reduced hydrogen bonding strength, and importantly PDP becomes soluble in PS at T > ca. 120 °C. At such temperatures PDP is found in both the P4VP and PS domains, thus leading to changes in the relative volume fractions of the domains, which in turn leads to order−order transitions. In PS-block-P4VP(MSA)1.0(PDP)1.0, typically lamellar and cylindrical block copolymeric structures were observed, where there was an additional internal lamellar order within the P4VP(MSA)1.0(PDP)1.0 domains. Coincidentally, an order−disorder transition within the P4VP(MSA)1.0(PDP)1.0 domains takes place at T = ca. 125 °C. Above that temperature, PDP is in both PS and P4VP(MSA)1.0 domains, but most interestingly at ca. T > 175 °C PDP becomes a nonsolvent for P4VP(MSA)1.0 and it is therefore expelled to predominantly to the PS domains. This manifests as an order−order transition. All samples exhibit at least two thermoreversible order−order transitions, and some of them show even five consecutive self-assembled phases as a function of temperature. Besides being amphiphilic, PDP can also be regarded as a plasticizer, i.e., relatively nonvolatile solvent, for the P4VP, PS, and P4VP(MSA)1.0 with cha...

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Section: Resultsmentioning

confidence: 99%

Self-Assembled Structures in Diblock Copolymers with Hydrogen-Bonded Amphiphilic Plasticizing Compounds

et al. 2006

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“…Even more complicated nanostructures have been created with block copolymers containing rigid moieties. [1,2] Another way to achieve mesomorphic structure at much smaller length scales is found in nonmesogenic amphiphilic oligomers which are noncovalently bonded to homopolymers [3] and block copolymers BCPs. [4] The dynamics of self-assembled nanostructures assume special importance in the context of producing functional macroscopic materials because self-assembly alone usually leads to polydomain structures with random orientations.…”

Section: Introductionmentioning

confidence: 99%

Rheology Pathway to Macroscale Ordered Nanostructures of Polymeric Nanotemplates: Nanopores, Nanosheets and Nanofibers

Fahmi

Gutmann

Vogel

et al. 2006

Macro Materials & Eng

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Summary: The creation of nanotemplates under dynamic shear flow conditions is described. The structures used are based on the self‐organization of comb‐coil‐like diblock copolymer systems with two intrinsic length scales, resulting from combining diblock copolymers with hydrogen‐bonding amphiphiles. Rheological data of polymeric supramolecular order formation are studied under oscillating shear flow conditions and it was observed that the order of the polymeric nanodomains can be extended to macroscopic distances. It is proposed that the key success factor to obtain highly ordered samples is to perform the orientation process using appropriate rheological conditions (temperature, frequency and strain) selected such that the ratio of the elastic component G′ to the viscous component G″ is larger than 1. This observation was used to select the rheological parameters for the three different samples investigated, where three different types of nanotemplates are observed after extracting the hydrogen‐bonding amphiphile; nanosheets, hollow cylinders and nanofibres. SAXS is primarily used to inspect the resulting structures. Additionally, AFM and TEM were utilized to image the morphologies and to further act as visual proof for the efficiency of the rheological orientation process.AFM phase image of PS‐b‐P4VP nanosheets on Si wafer substrate after extracting the PDP.magnified imageAFM phase image of PS‐b‐P4VP nanosheets on Si wafer substrate after extracting the PDP.

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“…[4 -6] A review summarizing the results of several research groups on this topic was given by Fischer and Poser. [7] An orientation of the morphology parallel to the smectic layers was found only in cases with oriented elliptical (deformed spherical), [8] cylindrical, [7] and lamellar domains. [9] Recently, a mixed orientation of smectic layers parallel and perpendicular to the interface was observed in a lamellar LC block copolymer.…”

Section: Introductionmentioning

confidence: 99%

Preparation of Oriented Liquid-Crystalline/Isotropic Block Copolymer Films with Parallel or Perpendicular Arrangement of Smectic Layers and Lamellar Microdomains

Figueiredo

Gronski²,

Bach

2002

Macromol. Rapid Commun.

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Liquid crystalline block and graft copolymers

Cited by 76 publications

References 87 publications

Self-Assembled Structures in Diblock Copolymers with Hydrogen-Bonded Amphiphilic Plasticizing Compounds

Self-Assembled Structures in Diblock Copolymers with Hydrogen-Bonded Amphiphilic Plasticizing Compounds

Rheology Pathway to Macroscale Ordered Nanostructures of Polymeric Nanotemplates: Nanopores, Nanosheets and Nanofibers

Preparation of Oriented Liquid-Crystalline/Isotropic Block Copolymer Films with Parallel or Perpendicular Arrangement of Smectic Layers and Lamellar Microdomains

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