Cyclopolymerizations: Synthetic Tools for the Precision Synthesis of Macromolecular Architectures

Abstract

Monomers possessing two functionalities suitable for polymerization are often designed and utilized in syntheses directed to the formation of cross-linked macromolecules. In this review, we give an account of recent developments related to the use of such monomers in cyclopolymerization processes, in order to form linear, soluble macromolecules. These processes can be activated by means of radical, ionic, or transition-metal mediated chain-growth polymerization mechanisms, to achieve cyclic moieties of variable ring size which are embedded within the polymer backbone, driving and tuning peculiar physical properties of the resulting macromolecules. The two functionalities are covalently linked by a "tether", which can be appropriately designed in order to "imprint" elements of chemical information into the polymer backbone during the synthesis and, in some cases, be removed by postpolymerization reactions. The two functionalities can possess identical or even very different reactivities toward the polymerization mechanism involved; in the latter case, consequences and outcomes related to the sequence-controlled, precision synthesis of macromolecules have been demonstrated. Recent advances in new initiating systems and polymerization catalysts enabled the precision syntheses of polymers with regulated cyclic structures by highly regio- and/or stereoselective cyclopolymerization. Cyclopolymerizations involving double cyclization, ring-opening, or isomerization have been also developed, generating unique repeating structures, which can hardly be obtained by conventional polymerization methods.

Cellulose Acetate Fabrics Loaded with Rhodamine B Hydrazide for Optical Detection of Cu(II)

“…These features can be ascribed to a high local concentration of the dye on the polymeric material [24]. Overall, the results testify the reaction of the deposited RBH with the Cu(II) ions present in solution, which leads to the opening of the spiro ring and formation of RB [25], and the trend in the absorption spectra points to a promising application of the prepared materials as colorimetric sensors for Cu(II). Moving towards a quantitative approach, the reflectance spectra have been converted in absorption spectra ( Figure S7): absorbance values of the order of 0.1 are detected for the RB band at 560 nm at the maximum concentration of Cu(II).…”

Unprecedented Sequence Control and Sequence‐Driven Properties in a Series of AB‐Alternating Copolymers Consisting Solely of Acrylamide Units

“…As the cyclopolymerization proceeds by an iterative intra‐ and intermolecular propagation, the tacticity of the resulting polymer after the cleavage could be different from that obtained by a conventional propagation process . As the tacticity could affect the physical properties, its characterization is important for the study of the sequence‐dependent properties.…”

“…As the cyclopolymerization proceeds by an iterative intraand intermolecular propagation, the tacticity of the resulting polymer after the cleavage could be different from that obtained by ac onventional propagation process. [36,37] As the tacticity could affect the physical properties,i ts characterization is important for the study of the sequence-dependent properties.T herefore,w ee xamined the tacticity of the resulting polymer by the conversion into HEAm homopolymers using 2-amino ethanol for the cleavage reaction, considering that it is difficult to characterize the tacticity of copolymers.F igure S4 in the Supporting Information shows the 13 CNMR spectra of the product (top) in comparison with poly(HEAm) synthesized via the radical polymerization of HEAm (bottom). Although some slight differences were observed, the peak shapes were almost identical, indicating similar tacticity to the polymer obtained by general propagation.…”

Complex polymer architectures through free-radical polymerization of multivinyl monomers

“…The historical development, the scope, the mechanism and the practical significance of cyclopolymerization have been summarized recently. 89 Here, we focus on the recently described monomer design strategies that facilitate intra-chain cyclization during radical cyclopolymerization.…”