Structure and Morphology of Poly(diethyl trimethylene-1,1-dicarboxylate) Crystals

Abstract

Poly(diethyl trimethylene-1,1-dicarboxylate) oligomers with an average degree of polymerization (DP) of 20 and a polydispersity of 1.13 have been isothermally crystallized at 30 °C from benzene and also crystallized from the melt (T m ) 176 °C). The crystals were investigated using electron microscopy (imaging and diffraction), X-ray diffraction, and computational modeling. The diffraction signals index on an orthorhombic unit cell with parameters a ) 1.554 ( 0.002 nm, b ) 1.136 ( 0.002 nm, and c (chain axis) ) 0.585 ( 0.002 nm. A space group of P212121 is assigned on the basis of systematic absences of h00, 0k0, and 00l for odd h, k, and l respectively; thus, two antiparallel chain segments pass through the basal ab plane of the unit cell. The calculated density of 1.20 g‚cm -3 is commensurate with the measured value of 1.17 ( 0.03 g‚cm -3 . The repetitive -CH2-CH2-CX2-backbone conformation, where the side groups X are ethyl esters (-COOC2H5), has the torsional angle sequence GTG h GTG h with the trans bonds at the dimethylene C-CH2-CH2-C sites. This conformation generates a 2-fold helix with a pitch that matches the measured crystallographic c-value of 0.585 nm. Ellipsoidal-shaped, lamellar-like crystals, with lateral dimensions on the micron scale but only 7.23 nm thick, are obtained by isothermal crystallization from benzene at 30 °C. Electron and X-ray diffraction data show that the molecular axes are orthogonal to the lamellar surface and that the crystal thickness matches a DP of 20. Thus, a degree of selective crystallization of molecular length occurs in these solution-grown crystals at fixed temperature. Under appropriate conditions, the crystals also stack to generate a one-dimensional lattice. This feature does not occur in the melt-crystallized fibers; in this case, the lamellar-like character is suppressed as the polydisperse molecules interpenetrate to form a crystal with a greater coherence length in the c-direction but, of course, with chain-end defects.

Metal‐Free Activation in the Anionic Ring‐Opening Polymerization of Cyclopropane Derivatives

“…[1][2][3] A few studies are available on the physicochemical properties exhibited by this class of unusual polymers. [4,5] The anionic ring-opening polymerization (ROP) of these monomers was performed in dimethyl sulfoxide (DMSO) using sodium or potassium thiophenolates as initiators. The livingness of the process was observed under appropriate experimental conditions, up to temperatures as high as 200 8C.…”

Synthesis, characterization, and ion-complexing properties of polymers displaying densely packed arrays of crown-ethers as lateral substituents

“…Due to the presence of quaternary carbons separated by CH 2 CH 2  linkers, OCDs such as Poly1 – Poly4 exhibit a strong tendency at adopting almost linear (all‐trans or g‐t‐g′) conformations, with geminal ester substituents extruding at 90° angles with respect to the vector defined by the linear polymer backbone and with neighboring C(COOR) 2 geminal ester pairs pointing in fully opposite directions and in an alternating fashion (see graphical abstract) . This unusual geometry is fully compatible with a regular placement of side substituents that optimizes intersubstituent distances and minimizes repulsive interactions while maintaining very high substitution densities.…”

Synthesis, Characterization, and Solid-State Properties of (CH2–CH2–C(COOH)2)n: A Highly Symmetrical, Semicrystalline Carbon-Chain Poly(carboxylic acid)

“…and Dimroth-Reichardt E T (30)), always include water at the top. 29 29 ; c for a polymer initial concentration of 10 g.L -1 , the following observations could be made after 2 hours: + clear solution, +/-suspension, -precipitation; d a test tube containing the initial solution/suspension was plunded in a water bath whose temperature wad rapidly raised from room temperature to the boiling point of the solvent; e at these temperatures, decarboxylation can possibly occur.…”

“…Further efforts are still in progress, in combination with simulations using as precursor the diethyl ester polymer whose crystal structure is known. 30 Films obtained by slow evaporation of either a saturated water solution or a 20 g.L -1 formamide solution on a glass slide led to cracked films that were examined under a polarized light microscope (Figures S5-S7 in the Supporting Information). As expected from optically anisotropic crystalline materials, significant amounts of the solid exhibited birefringence.…”