Living cationic polymerization of vinyl ethers with a naphthyl group: Decisive effect of the substituted position on naphthalene ring

Abstract

Living cationic polymerization of a vinyl ether with a naphthyl group [2‐(2‐naphthoxy)ethyl vinyl ether, βNpOVE] was achieved using base‐assisting initiating systems with a Lewis acid. The Et1.5AlCl1.5/1,4‐dioxane or ethyl acetate system induced the living cationic polymerization of βNpOVE in toluene at 0 °C. The living nature of this reaction was confirmed by a monomer addition experiment, followed by 1H NMR and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) analyses. In contrast, the polymerization of αNpOVE was not fully controlled; under similar conditions, it produced polymers with broad molecular weight distributions. The 1H NMR and MALDI‐TOF‐MS spectra of the resultant poly(αNpOVE) revealed that the products had undesirable structures derived from Friedel–Crafts alkylation. The higher reactivity of αNpOVE in electrophilic substitution reactions, such as the Friedel–Crafts reaction, was attributable to the greater electron density of the naphthyl ring, which was calculated based on frontier orbital theory. The naphthyl groups significantly affected the properties of the resultant polymer. For example, the glass transition temperatures (Tg) of poly(NpOVE)s are higher by approximately 40 °C than that of poly(2‐phenoxyethyl vinyl ether). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Precision synthesis of graft copolymers via living cationic polymerization ofp-acetoxystyrene followed by friedel-crafts-type termination reaction

“…The naphthyl group was expected to function as a Friedel–Crafts‐type quencher because of its high nucleophilicity. We have previously demonstrated that a well‐defined poly(βNpOVE) could be synthesized by a base‐assisting living cationic polymerization with the IBEA/Et 1.5 AlCl 1.5 initiating system …”

“…More reactive aromatic rings such as a naphthyl group could allow more facile synthesis of well‐defined polymers in cationic polymerization. Thus, we started investigating precision synthesis via cationic polymerization of naphthyl‐containing monomers, and have reported the living cationic polymerization of monomers with a naphthyl ring, despite its high reactivity in the electrophilic substitution reactions owing to more expanded conjugated system than a phenyl ring …”

“…Thus, we focused on the synthesis of graft copolymers using a naphthyl group‐containing polymer as a macroterminator. This strategy does not require any functionalization of the side chains because the macroterminator, a well‐defined polymer with naphthyl reactive groups, is directly obtained by the base‐assisting living cationic polymerization …”

Syndioselective Polymerization of Vinylnaphthalene

“…Poly(vinylnaphthalenes) have become of interest owing to their potential applications as fluorescence tags and electron beam lithography resists as well as their interesting photophysical characteristics . However, the well‐controlled polymerization of vinylnaphthalene derivatives remains challenging since the uneven electron density distribution makes naphthalene highly susceptible to nucleophilic reagents and Friedel–Crafts reaction . Therefore, the polymerization of vinylnaphthalene monomers encounters great difficulty via cationic, anionic, and radical mechanisms .…”

“…The coordination polymerization of 1VN was first examined at room temperature by using precursor 1 based catalytic system (Figure ) and a moderate activity was observed (1.44 × 10 5 g (mol Ln h) −1 ; Table 1 , run 1) although the catalyst show extremely high activity and syndio‐selectivity for styrene polymerization . Unexpectedly, the GPC curve of the resulting product gives pronounced multimodal peaks with a very broad molecular weight distribution (PDI = 54.9; Table , run 1; Figure ; Figure S26, Supporting Information), which was probably caused by addition‐alkylation reactions because of the high reactivity of naphthalene ring to the strong Lewis acidic active species . The pyridyl side‐armed fluorenyl scandium precursor 2a , a highly active and syndioselective catalyst for styrene polymerization also, was employed to initiate 1VN polymerization.…”