Alternating deposition multilayer films of dendrimers/poly(4-vinylpyridine) based on hydrogen bonding

Abstract

Layer-by-layer (LbL) assembly technique has been an important method for constructing layered nanostructural materials. Although the electrostatic interaction is the primary driving force for building LbL multilayers, our group and other group have reported early that hydrogen bonding interaction can be also used as the driving force. One of the advantages of preparing multilayers via hydrogen bonding is that the assembly process can be performed in organic solvent which enables the water-insoluble species assembling. Moreover, hydrogen bonding is sensitive to pH value which could functionalize the multilayers. For example, Granick et al. prepared erasable hydrogen-bonded ultrathin polymer film, Caruso et al. fabricated deconstructible polymeric film, and Rubner et al. recently created stable superhydrophobic multilayers. Zhang et al. also produced microporous films through post-base treatment of the hydrogen-bondMultilayer assemblies were prepared by alternating deposition of An(G1) ing-directed LbL multilayers. However, bis-functional hydrogen-bonding donor and acceptor failed to fabricate LbL multilayer, because their interaction is probably not strong enough. Herein different generations of Frechet-type dendrimers with carboxyl groups at the periphery and diphenylanthracene core were designed and synthesized (Scheme 1). This allows us to study effects of the generation number of dendrimer on LbL assembly. Two dendrimers were synthesized with a similar route in ref. [12], and noted An(G1)4 and An(G2)4. They were achieved through coupling reaction of 9,10-bis (3,5-dihydroxyphenyl)anthracene (An) with Frechet-type dendrons of generation one((MeO2C)2-[G1]-Br) and generation two ((MeO2C)4-[G2]-Br), respectively. Methyl ester groups at the periphery of the dendrimers were changed to carboxyl groups by hydrolysis and acidification. The characterization data are shown below: An(G1)4: H NMR (500 MHz, DMSO-d6): δ7.93 (16H, d, ArH), δ 7.57 (4H, m, core ArH), δ 7.51 (16H, d, ArH), δ 7.32 (4H, m, core ArH), δ 6.88 (2H, s, ArH), δ 6.75 (8H, bs, ArH), δ 6.68 (4H, bs, ArH), δ 6.66 (4H, s, ArH), δ 5.15 (16H, s, OCH2), δ 5.10 (8H, s, OCH2), MALDI-TOFMS: Calc. for C118H90O28 [M+H]: m/z 1956.96, found [M+H]: m/z 1956.4. An(G2)4: H NMR (500 MHz, DMSO-d6): δ 7.90 (32H, d, ArH), δ 7.58 (4H, m, core ArH), δ 7.47 (32H, d, ArH), δ 7.32 (4H, m, core ArH), δ 6.88 (2H, s, ArH), δ 6.68 (24H, bs, ArH), δ 6.66 (4H, s, ArH), δ 6.60 (8H, s, ArH), δ 6.58 (4H, s, ArH), δ 5.10 (32H, s, OCH2), δ 5.06 (8H, s, OCH2), δ 4.96 (16H, s, OCH2), MALDI-TOFMS: Calc. for C238H186O60 [M+Na]: m/z 4028.99, found [M+Na]: m/z 4028.7.