Synthesis of polymers with hydroxyl end groups by atom transfer radical polymerization

Abstract

SUMMARY: Polymers prepared by atom transfer radical polymerization (ATRP) contain end groups defined by the initiator used. Alkyl halides, used as initiators, lead to polymers with an alkyl group at one end and a halide as the other chain end. Using functionalized initiators such as 2-hydroxyethyl 2-bromopropionate, hydroxyl groups can be directly incorporated at one polymer chain end while the other end functionality remains a halogen. The direct displacement of the halogen end groups with hydroxyl groups was unsuccessful due to side reactions such as elimination (for polystyrene) or hydrolysis of ester functions (for polyacrylate). Another approach to generate hydroxyl end groups was based on the substitution of the halogen end groups by ethanolamine. This was successful for polystyrene but additional substitution at the backbone esters was observed in polyacrylates. Multiple substitution reactions could be avoided by using 4-aminobutanol instead of 2-aminoethanol. Hydroxyl terminated polyacrylates were also obtained by extending the polyacrylate chain end with one allyl alcohol unit in a one-pot process by adding an excess of allyl alcohol at the end of e polymerization of acrylate.

Theoretical and Experimental Studies on Elementary Reactions in Living Radical Polymerization via Organic Amine Catalysis

“…When primary amines (RNH 2 ) are used, a side reaction, i.e., a substitution reaction of iodine of PMMA-I with RNH 2 to generate polymer–NHR (chain-end transformation), can be significant. This side reaction is much faster for primary amines than secondary and tertiary amines and is usually unimportant for tertiary amines.…”

2-Azaallyl Anion Initiated Ring-Opening Polymerization of N-Sulfonyl Aziridines: One-Pot Synthesis of Primary Amine-Ended Telechelic Polyaziridines

“…Telechelic polymers, bearing at least two reactive end groups, are important building blocks for various macromolecular architectures through cross-linking, chain extension, etc . Many industrially important materials, such as block copolymers, networks, elastomers, macromonomers, surfactants, are derived from the telechelic polymers. , For the synthesis of such valuable telechelics, the reactive end groups are usually introduced to the chain either by using functional initiators or terminating the living chains with a switchable electrophile. − Until now, significant achievements have been made in telechelic polymer synthesis with the incorporation of many reactive functionalities (e.g., −OH, −COOH, −halide, and −allyl). , Among them, the synthesis of well-defined telechelic polymers with primary amine chain ends is of great importance due to the amino groups having a great utility ranging from modified functional surfaces to various biomedical applications. − …”

Molecular Weight Distribution of Living Chains in Polystyrene Prepared by Atom Transfer Radical Polymerization

“…Atom transfer radical polymerization (ATRP) is a useful method to obtain polymers with a narrow molecular weight distribution (MWD) , and various chain end functionalities (CEF). − While polymer chains are growing in ATRP, dead chain formation is unavoidable, albeit suppressed, due to the termination reaction between the free radicals as well as side reactions such as loss of HBr from the chain ends that are responsible for imperfect CEF and a broader MWD than a living anionic polymerization. − The dead chain fraction is affected by various factors including the rates of polymerization, the monomer conversion, the target degree of polymerization, and so on. − The imperfect living nature of ATRP limits the purity in the synthesis of block copolymers , and topological polymers. , There are a few theoretical/simulation studies on the MWD of ATRP polymers, − but the precise MWD of polymers prepared by ATRP is yet to be addressed experimentally since the ATRP polymers has an overlapped MWD of both living and dead chains.…”