Mixtures of an Acid-Functionalized Mesogen with Poly(4-vinylpyridine)

Abstract

A thermotropic dialkoxy biphenyl liquid crystal, functionalized by a carboxylic acid group at one extremity, is mixed to varying proportions with poly(4-vinylpyridine) (P4VP). The liquid crystal, LC-4,6A, is characterized by a monotropic smectic A phase and a highly ordered or crystalline lamellar phase formed primarily of acid dimers. In the mixtures with P4VP (studied up to acid/pyridine molar ratios of 1.0), the fluid mesophase is suppressed. A solidisotropic phase transition is present above a molar ratio of about 0.2, whereas for lower LC-4,6A contents the mixtures form an apparently miscible, amorphous material. The glass transition temperature, T g , of the latter is strongly depressed, at a rate of 7 °C/mol % LC-4,6A up to a molar ratio of 0.1, after which the T g remains essentially constant. As supported by infrared analysis, the plasticization behavior is attributed to strong hydrogen bonding between the acid and pyridine moieties, which solubilizes the LC-4,6A molecules within the polymer matrix. When the solubility limit is reached, the excess small molecule solidifies into an ordered phase that is essentially identical to that of neat LC-4,6A. This phase can be modified by quenching from the melt, which freezes in a greater proportion of the acidpyridine interactions and leads to incorporation into this phase of significant amounts of P4VP.

Funktionelle flüssigkristalline Aggregate: selbstorganisierte weiche Materialien

“…Die Polymerkomplexe 18 [102] und 19 [103,104] wurden durch Komplexierung von endständig funktionalisierten Mesogenmolekülen und rück-gratfunktionalisierten Polymeren wie Poly(vinylpyridin) oder Poly(acrylsäure) erhalten. [105][106][107][108] Nichtmesogene Alkylphenole bilden ebenfalls mesogene Komplexe 20.…”

Supramolecular Assemblies from Poly(styrene)-block-poly(4-vinylpyridine) Diblock Copolymers Mixed with 6-Hydroxy-2-naphthoic Acid

“…After washing with methanol, this peak again shifts to the initial value corresponding to the pure PS-b-P4VP block copolymer film, due to complete removal of the HNA from the P4VP + HNA phase. The formation of H-bonds is further evidenced by the characteristic peaks shown in Figure 2b for HNA (corresponding to not-bound -COOH group) shifted to 1697 cm −1 , because of hydrogen bond formation between the carboxylic acid groups and the pyridine moieties of the P4VP blocks [39][40][41]. Finally, the two broad bands observed at around 2500 cm [40,42].…”

“…In this scenario, the accordingly formed micellar core is stabilized by coronal chains from the remaining uncomplexed soluble blocks of the starting block copolymer. This strategy has been widely used to form electrostatic complexes from a polyelectrolytic block and oppositely charged surfactant molecules, as reported by several groups in the mid-1990s [39][40][41].…”

Functional liquid-crystalline polymers and supramolecular liquid crystals

“…37 A variety of polysiloxane-based [50][51][52] and polyacrylate-based 53,54 side-chain LC polymers have been obtained by the formation of supramolecular mesogens through a variety of hydrogen bonds. Nonmesogenic poly (vinylpyridine) (PVP) [55][56][57][58][59] and poly(acrylic acid) (PAA) 60 were also used to prepare LC polymers by the complexation with complementary hydrogen-bond donors or acceptors. A main-chain polyamide incorporating 2,6-bis(amino)pyridine units can form supramolecular complexes with a biphenylcarboxylic acid.…”