Quantification of ATRP initiator density on polymer latex particles by fluorescence labeling technique using copper-catalyzed azide-alkyne cycloaddition

Abstract

We developed a novel fluorescence labeling technique for quantification of surface densities of atom transfer radical polymerization (ATRP) initiators on polymer particles. The cationic P(St-CPEM-C 4 DMAEMA) and anionic P(St-CPEM) polymer latex particles carrying ATRP-initiating chlorine groups were prepared by emulsifier-free emulsion polymerization of styrene (St), 2-(2-chloropropionyloxy)ethyl methacrylate (CPEM), and N-n-butyl-N,N-dimethyl-N-(2-methacryloyloxy)ethylammonium bromide (C 4 DMAEMA). ATRP initiators on the surface of polymer particles were converted into azide groups by sodium azide, followed by fluorescent labeling with 5-(N,Ndimethylamino)-N 0 -(prop-2-yn-1-yl)naphthalene-1-sulfonamide (Dansyl-alkyne) by copper-catalyzed azide-alkyne cycloaddition (CuAAC). The reaction time required for both azidation of ATRP-initiating groups and successive fluorescence labeling of azide groups with Dansyl-alkyne by CuAAC were investigated in detail by FTIR and fluorescence spectral measurement, respectively. The ATRP initiator densities on the cationic P(St-CPEM-C 4 DMAEMA) and anionic P(St-CPEM) particle surfaces were estimated to be 0.21 and 0.15 molecules nm 22 , respectively, which gave close agreement with values previously determined by a conductometric titration method. The fluorescence labeling through click chemistry proposed herein is a versatile technique to quantify the surface ATRP initiator density both on anionic and cationic polymer particles.

Thermoresponsive Polymer Brushes on Organic Microspheres for Biomolecular Separation and Immobilization

“…Using this method, we were able to estimate the densities of ATRP initiators on the crosslinked core and the successful PM@alkyne2 particles to be 0.36 and 0.25 mol nm −2 , respectively. These values are calculated by using a particle core diameter of 1.90 µm and are found to be similar to that reported previously in the literature . We should note that the density of 0.25 initiator molecules nm −2 on the PM@alkyne2 particles may be a somewhat underestimated value, because part of the internal alkyne groups in the polymer brushes may react with the terminal azide.…”

“…These values are calculated by using a particle core diameter of 1.90 µm and are found to be similar to that reported previously in the literature. [34,35] We should note that the density of 0.25 initiator molecules nm −2 on the PM@ alkyne2 particles may be a somewhat underestimated value, because part of the internal alkyne groups in the polymer brushes may react with the terminal azide. It is also possible that due to steric hindrance, the alkyne-FITC adduct used in this work may not react with all the azides converted from the ATRP initiators.…”

Preparation of polymer latex particles carrying salt-responsive fluorescent graft chains

“…The surface ATRP initiator density is one of the most important colloidal properties of grafted polymer particles. In general, the density of surface ATRP initiating groups can be suitably measured by conductometric titration [54] or fluorescence technique [55]. The ATRP initiating group density at the surface of anionic SC particles was measured to be 0.11 groups/ nm 2 by conductometric titration.…”

“…The copolymerized amount of CiBM was calculated by 1 H NMR spectrum measurement as reported in our previous paper [55]. Fig.…”

Synthesis of luminescent core–shell polymer particles carrying amino groups for covalent immobilization of enzymes

“…In particular, (meth)acrylates with α-haloester groups in the side chain can be copolymerized with other monomers, paving the way for the synthesis of graft polymers with branched chains through the ATRP mechanism [45]. This method can also be applied to the synthesis of core-shell particles by graft polymerization from the surface of polymer core particles, so-called surface-initiated ATRP (SI-ATRP) [46][47][48][49][50][51][52][53][54][55]. Several kinds of functional groups can be introduced at both the α-and ω-termini of linear polymers synthesized by ATRP [56][57][58][59][60][61]; the functional groups can be introduced to only the ω-termini of polymer chains grafted from the solid surface.…”