Linear, Single-Strand Heteroaromatic Polymers from Superacid-Catalyzed Step-Growth Polymerization of Ketones with Bisphenols

Abstract

Novel, linear, high-molecular-weight single-strand heteroaromatic polymers and copolymers containing 9H-xanthene moieties in the backbone were synthesized by metal-free superacid-catalyzed stoichiometric and nonstoichiometric step-growth polymerizations of carbonyl compounds bearing electron-withdrawing substituents with bisphenols. The electrophilic aromatic substitution reactions of ketones with phenol fragments occur exclusively in ortho-positions to the hydroxy phenol group and followed by highly efficient cyclodehydration reaction of hydroxyl-containing intermediates to give corresponding substituted 9H-xanthene-2,7-diyl polymers. The polymerizations were performed at room temperature in the Brønsted superacid trifluoromethanesulfonic acid (CF 3 SO 3 H, TFSA) and in a mixture of TFSA with methylene chloride and nitrobenzene.

Modeling of Superacid Catalyzed Step‐Growth Polymerization of Isatin and Biphenyl or Terphenyl Monomers

“…Although it has been proposed that superacid catalyzed polyhydroxyalkylations deviate significantly from the classical behavior of A 2 + B 2 step‐growth polymerizations, there are no kinetic modeling studies, focused on molecular weight development, reported for this system, which can explain such deviations. It is our objective in this contribution to propose a kinetic model for superacid catalyzed polyhydroxyalkylations focused on molecular weight development.…”

“…Since the reaction proceeds between A and B only (A does not react with itself and the same occurs with B), this will result in a reduction of molecular weight. However, in superacid catalyzed polyhydroxyalkylations the experimental evidence shows that increasing the excess of one of the functional groups (isatin), which is equivalent to decreasing r in Equation , will result in an increase in molecular weight . In order to account for this observation, in this work we assumed that the four reactions of the polymerization scheme shown in Equations – react at different rates, namely, instead of having a single kinetic rate constants, k , we have four: k ab , k am , k bm , and k mm .…”

“…Zolotukhin and co‐workers developed a superacid catalyzed polyhydroxyalkylation novel synthetic route (see Figure ), which can be classified as an unusual A 2 + B 2 step‐growth polymerization since ultrahigh molecular weights and molar mass dispersities ( Ð ) less or higher than two are possible, at nonstoichiometric conditions. The dramatic acceleration in polymerization rate observed in superacid catalyzed polyhydroxyalkylations with a small excess of the carbonyl compound is known as the “nonstoichiometric effect.” Superacid catalyzed polyhydroxyalkylations have the following advantages: (i) the reaction proceeds at room temperature and atmospheric pressure, (ii) structural variety and commercial availability of monomers, (iii) high conversion yields, (iv) high regioselectivities, (v) acceptable reaction times, (vi) great versatility in polymer architectures, (vii) functional groups that allow polymer chemical modification reactions, (viii) easy polymer purification, (ix) good physical, chemical, and thermal properties of the produced polymers, and (x) high polymer molecular weights.…”

Super acid-catalyzed polymerization of phenothiazine and modified isatin

“…Super acid-catalyzed (Friedel-Crafts aromatic electrophilic substitution reaction) reaction has gaining remarkable interest in recent past [19][20][21][22][23][24] because of their myriad advantages associated with eco-friendliness. Super acidcatalyzed reactions have the following advantages: the reaction proceeds at room temperature, structural selection and easy availability of monomers, high yields and selectivity, short duration of reaction, more versatility in polymer architectures, easy purification, possessing good physical, chemical, and thermal properties of the synthesized polymers, and high molecular weights, etc.…”

“…Consequently, several reactions have been performed using super acids [mostly trifluoromethanesulfonic acid (TFSA)] and open up a new avenue in chemistry. The dramatic use of super acid catalyst in hydroxyalkylation reactions [29], polyhydroxyalkylation [20], and synthesis of hyper-branched polymers [19,38] was progressively reported.…”