Pd complexes with a chelating diimine ligand promote ring-opening polymerization of 2-alkoxy-1-methylenecyclopropanes to produce the polymers having vinylidene and alkoxy substituents for every threecarbon unit. 13 C{ 1 H} NMR spectra of the produced polymers show the well-regulated structures with head-totail connection of the repeating units. [(π-Allyl)PdCl] 2 initiates living polymerization of 2-alkoxy-1methylenecyclopropanes (alkoxy: OBu, O t Bu, OMe) to afford the polymers with narrow molecular weight distribution. Molecular weight of the polymer was controlled over a wide range by changing the initial monomerto-initiator molar ratio. Direct measurement of the growing polymer of 2-butoxy-1-methylenecyclopropane by NMR and GPC indicates that the polymer molecule has a dimer structure with a Pd 2 Cl 2 core and two π-allyl-Pd bonds. Treatment of the growing polymer with nucleophilic reagents, such as NaOH/MeOH, NaOH/H 2 O, AgOAc, and NaCMe(COOEt) 2 -PPh 3 , cleaves the π-allyl-Pd bonds and forms the polymers having organic functional groups at the terminal. The macromonomer having an R,β-unsaturated aldehyde terminal copolymerizes with styrene in the presence of AIBN to afford the polymer having oligo(1a) side chains. Photoirradiation of the polymer of 2-butoxy-1-methylenecyclopropane having the π-allyl-Pd bonds in the presence of chelating N-ligands causes coupling of the π-allylic polymer ends to produce the organic polymer.
The polymers with functionalized alkoxy groups and with narrow molecular weight distribution (Mw/Mn < 1.12) are obtained from the living polymerization of 2‐alkoxy‐1‐methylenecyclopropanes using π‐allylpalladium complex, [(PhC3H4)Pd(μ‐Cl)]2, as the initiator. The polymers with oligoethylene glycol groups in the alkoxy substituent are soluble in water, and hydroboration of the CC double bond and ensuing addition of the OH groups to CN bond of alkyl isocyanate produce the polymers with urethane pendant groups. The reaction decreases solubility of the polymer in water significantly. Di‐ and triblock copolymers of the 2‐alkoxy‐1‐methylenecyclopropanes are prepared by consecutive addition of the two or three 2‐alkoxy‐1‐methylenecyclopropane monomers to the Pd initiator. The polymers which contain both hydrophobic butoxy or tert‐butoxy group and hydrophilic oligoethylene glycol group dissolve in water and/or organic solvents, depending on the substituents. The 1H NMR spectrum of poly(1a‐b‐1h) ((CH2C(CH2)CHOBu)n(CH2C(CH2)CH(OCH2CH2)3OMe)m) in D2O solution exhibits peaks because of the butoxy and CH2 hydrogen in decreased intensity, indicating that the polymer forms micelle particles containing the hydrophilic segments in their external parts. Aqueous solution of the polymer with a small amount of DPH (DPH = 1,6‐diphenyl‐1,3,5‐hexatriene) shows the absorbance due to DPH at concentration of the polymer higher than 5.82 × 10−5 g mL−1. Other block copolymers such as poly(1b‐b‐1h) and poly(1a‐b‐1g) also form the micelles that contain DPH in their core. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 959–972, 2009
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