Georgeta Caraculacu

The heterocyclization of several reactive polymers Poly(parabanic acids)

Abstract Some poly(parabanic acids) were synthesized by intermolecular reaction between the urea group from polyureas and oxalyl chloride in the presence of pyridine as catalyst. All the synthesized polyureas and poly(parabanic acids) were characterized by thermogravimetric, i.r. and elemental analysis.

Dibenzyl structure on the macromolecular chain—IV. Polyureas and poly(parabanic acid)s☆

Abstract Polyureas with the dibenzylic system on the macromolecular chain are considered. The behaviour of these polyureas during cyclization with oxalyl chloride, leading to polyparabanic derivatives, was studied. The influences of polymer structures and reaction conditions on the heterocyclization is discussed. All the polymers were characterized by elemental analyses, inherent viscosities, i.r. spectra and thermogravimetric analyses.

Poly(parabanic acid)s. New aspects of structure–properties relationships

Abstract Polymers with parabanic units in the macromolecular chain were prepared by intermolecular reaction between various polyureas and oxalyl chloride. The influence of polymer structure on the heterocyclization process and on the properties of the resulting polymers are discussed. All polymers were characterized by elemental and thermogravimetric analyses, inherent viscosities, IR spectra, differential scanning calorimetry, X-ray diffraction, and electrical conductivity measurements.

Polyhydrazides and poly(1,3,4-oxadiazole)s with parabanic structures

Abstract Polyhydrazides with parabanic structures were prepared by polycondensation between a new monomer containing a preformed parabanic ring, viz. 1,3 p (bis-chloroformylphenyl) parabanic acid and dihydrazides. By thermal cyclization with polyphosphoric acid, the polyhydrazides were converted to poly(1,3,4-oxadiazole)s with parabanic structures. The films obtained from these polymers exhibit electrical insulating properties and good thermal stability.

Dibenzylic structures on macromolecular chain: IX. The interaction of urethane-isocyanate groups in polyurethane formation

Abstract The interaction of isocyanate-urethane and isocyanate-amide groups in urethane group formation is studied. Bibenzil-2,2′-di-yl diisocyanate (2,2′ BBDI) presents specific behaviour due to the steric specificity of its structure. Rotation of the two aromatic nuclei around ethylenic bridges favours strong intramolecular anchimeric assistance in the second step of the 2,2′ BBDI with n -butanol (BuOH) reaction. This assistance also enhances secondary reactions leading to unexpected cyclic allophanate structure. Mechanisms for these reactions are proposed in concordance with kinetic measurements.

The heterocyclization of some reactive polymers by a 3 + 2 dipolar cyclo-addition reaction—II. Polyamides and polyhydrazides

Abstract Based on quantitative transformation of unsaturated polyesters into Δ 2 -pyrazoline polymers when reacted with 1,3-dipoles, attempts were made to apply the same reaction to unsaturated polyamides and polyhydrazides having double bonds conjugated with a carbonyl group. One could not obtain heterocyclic polymers because of factors discussed in the paper. The presence of an active hydrogen atom in the molecule of polyamide or polyhydrazide causes a decrease of the dipolarophile capacity of the double bond. Substitution of these hydrogen atoms, both in model compounds and polymers, leads to the expected results. Thus N -alkylpolyamide was quantitatively transformed into the Δ 2 -pyrazoline polyamide.

Synthesis of metal containing polyureas with a parabanic structure

A new diisocyanate containing a parabanic ring was synthesized via a Curtius rearrangement reaction. The direct reaction of this diisocyanate with the Mg salt of p-aminobenzoic acid, or with a mixture of aromatic diamines gave ionic polyureas with a parabanic structure. A detailed study of inherent viscosities of these polymers was achieved.

New Parabanate Products by 1, 3-Dipolar Cycloaddition Reaction (‘Criss-Cross’ Cycloaddition):

New parabanate products containing 1, 3, 5, 7-tetraazabicyclo[3, 3, 0]octane-2, 6-dione are described. The synthesis of αω-diisocyanato-telechelics starting from two diisocyanates having a preformed parabanic unit using a [3+2] dipolar cycloaddition reaction was studied. The obtained products were characterized by IR spectroscopy, elemental and thermogravimetric analyses and solubility tests. The proposed structure was confirmed by analytical data.