Supramolecular Tubular Structures of a Polymethacrylate with Tapered Side Groups in Aligned Hexagonal Phases

Abstract

X-ray methods have been used to analyze the supramolecular tubular structures in the hexagonal solid state and columnar hexagonal liquid crystalline ( &, ) phases of a polymethacrylate with tapered side groups: specific~y,poly(2-(2-[2-(2-(methacryloyloxy)ethoxy)ethoxylethoxy)ethyl3,4,5-tris(@-(dodecyloxy)-benzyl)oxy)benzoate), abbreviated as 12-ABG-4EO-PMA. Oriented fibers were drawn from the liquid crystalline phase at -60 O C and annealed for several days at 4 "C. The X-ray pattern for these fibers recorded at room temperature (25 "C) contained eight equatorial reflections that are orders predicted for a hexagonal unit cell with a = b = 60.4 A. The similarity of the data to those for unoriented specimens in the & phase suggests that both phases contain the same type of supramolecular cylindrical moieties. In addition, wideangle maxima are observed on the equator and two layer lines that suggest formation of a three-dimensionallyordered structure at room temperature. These data give the first available information on the supramolecular structure within the columns. The layer line spacings define a repeat of c = 5.03 A along the column axis, containing eight monomeric units based on the observed density. Strong off-meridional maxima at d = 4.30 and 3.84 A on the first layer line suggest that the "planes" of the aromatic moieties are tilted rather than perpendicular to the cylinder axis. Possible "pine tree" models are discussed in which the tapered side groups are stacked in 8-fold layers or form &fold helices within the columns. Increasing the temperature to 60 O C leads to a reduction in the cylinder diameter to 58.0 A. Stacking correlations remain along the fiber axis direction, but otherwise the internal structure of the cylinder is muchmore disordered than at room temperature. On cooling, the three-dimensional order is restored.

New Developments in Polymer Analytics II

“…61a depicts different length values derived from SFM, SEC and SLS experiments. In agreement with the Xray data [37,597], the SFM length per monomer unit of polymer 1 (l SFM =1.2 Å) turned out to be almost two times less than the length for a fully extended main chain (l c =2.5 Å) in an all-trans conformation. The axial contraction was attributed to a locally coiled or twisted conformation of the backbone (Fig.…”

Transformation of a Spherical Supramolecular Dendrimer into a Pyramidal Columnar Supramolecular Dendrimer Mediated by the Fluorophobic Effect

“…The other model, known as the pine-tree columnar model, results from a helical pine-tree-like arrangement of tapered dendrons that are tilted with respect to the column axis and also rotated about the molecular long axis. [11] In this model, three dendrons with all the benzyl ethers in trans conformations are located nearly at the same position along the column axis to form a nonhelical pine-tree-like cone with a total vertical thickness of nearly 3 4.8 ( Figure 1, Figure 3 b). Density calculations show that each dendron partially occupies three neighboring conical strata of thickness 4.8 (see Supporting Information).…”

Origin of Bends in Unperturbed Vinyl Polymers: An Illustration with Polystyrene

“…If this interpretation is correct, control of the bends requires control of temporal fluctuations. An alternative explanation would be based on the generally atactic nature of the dendronized polymers derived from polymers such as polystyrene (PS)1–3, 5–17 or poly(methyl methacrylate) 1, 3, 5, 16, 18–22. It assumes that certain stereochemical sequences in localized parts of the chain create a propensity for the formation of a bend at these sites.…”