Amphiphilic Copolymer of Poly(ethylene glycol)-<I>Block</I>-Polypyridine; Synthesis, Physicochemical Characterization, and Adsorption Onto Silica Nanoparticle
作者:Daisuke Matsukuma、Yukie Maejima、Yusuke Ikenaga、Taketomo Sanbai、Koji Ueno、Hidenori Otsuka
DOI:10.1166/jnn.2014.9366
日期:2014.9.1
In this study, we newly synthesized amphiphilic block copolymers composed of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic pyridine segments (PEG-b-Py). Chain transfer agent terminated PEG was subsequently chain-extended with 3-(4-pyridyl)-propyl acrylate to obtain PEG-b-Py by reversible additional-fragmentation chain transfer (RAFT) polymerization. Particularly, the effect of varying PEG molecular weight (Mn ) of the block copolymers (Mn =2000 (2k), and 5000 (5k)) was investigated in terms of critical micelle concentration (cmc), pyrene solubilization, micelle size distribution, and association number per micelle. Based on the amphiphilic balance, PEG-b-Pys formed core-shell type polymer micelle. The cmc value of PEG2k-b-Py was lower than that of PEG5k-b-Py, suggesting the degree of phase separation was strongly depended on PEG Mn . Furthermore, the adsorption of PEG-b-Py copolymer onto silica nanoparticles as dispersant was studied to estimate the effect of PEG Mn in the copolymers and their solubility in the medium on the adsorption. Adsorbed density of PEG2k-b-Py copolymer onto silica nanoparticle was higher than that of PEG5k-b-Py, which was significantly correlated with the degree of phase-separation based on the amphiphilic balance. The adsorbed amount of copolymer was further changed as a function of solvent polarity, phase separation predicting the presence of the acid-base interaction between Py and silanol group existed on silica nanoparticles. The resultant dispersion stability was highly correlated with the graft density of copolymer onto silica surface. As a result, PEG2k-b-Py coated silica nanoparticles in aqueous media (with high solvent polarity) showed high dispersion stability. These fundamental investigations for the surface modification of the nanoparticle provide the insight into the highly stable colloidal dispersion as well as the design of dispersant molecular structure.
在这项研究中,我们新合成了由亲水性聚乙二醇(PEG)和疏水性吡啶片段(PEG-b-Py)组成的两亲性嵌段共聚物。随后,通过可逆附加片段链转移(RAFT)聚合,用3-(4-吡啶基)-丙烯酸丙酯对端链转移剂终止的PEG进行链扩展,得到PEG-b-Py。特别地,从临界胶束浓度(cmc)、芘增溶、胶束尺寸分布和每个胶束的缔合数等方面研究了嵌段共聚物中PEG分子量(Mn)的变化(Mn =2000(2k)和5000(5k))的影响。基于两亲性平衡,PEG-b-Pys形成了核壳型聚合物胶束。PEG2k-b-Py的cmc值低于PEG5k-b-Py的cmc值,表明相分离程度与PEG Mn密切相关。此外,研究了PEG-b-Py共聚物作为分散剂吸附到二氧化硅纳米颗粒上的情况,以评估共聚物中PEG Mn的影响及其在介质中的溶解度对吸附的影响。PEG2k-b-Py共聚物吸附到二氧化硅纳米颗粒上的密度高于PEG5k-b-Py,这与