Article Metrics


Online attention

How do spherical diblock copolymer nanoparticles grow during RAFT alcoholic dispersion polymerization?

DOI: 10.1021/acs.macromol.5b02385 DOI Help

Authors: E. R. Jones (University of Sheffield) , O. O. Mykhaylyk (University of Sheffield) , M. Semsarilar (DSM Ahead) , M. Boerakker (DSM Ahead) , P. Wyman (DSM Ahead) , S. P. Armes (University of Sheffield)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Macromolecules , VOL 49 (1) , PAGES 172 - 181

State: Published (Approved)
Published: January 2016

Open Access Open Access

Abstract: A poly(2-(dimethylamino)ethyl methacrylate) (PDMA) chain transfer agent (CTA) is used for the reversible addition–fragmentation chain transfer (RAFT) alcoholic dispersion polymerization of benzyl methacrylate (BzMA) in ethanol at 70 °C. THF GPC analysis indicated a well-controlled polymerization with molecular weight increasing linearly with conversion. GPC traces also showed high blocking efficiency with no homopolymer contamination apparent and Mw/Mn values below 1.35 in all cases. 1H NMR studies confirmed greater than 98% BzMA conversion for a target PBzMA degree of polymerization (DP) of up to 600. The PBzMA block becomes insoluble as it grows, leading to the in situ formation of sterically stabilized diblock copolymer nanoparticles via polymerization-induced self-assembly (PISA). Fixing the mean DP of the PDMA stabilizer block at 94 units and systematically varying the DP of the PBzMA block enabled a series of spherical nanoparticles of tunable diameter to be obtained. These nanoparticles were characterized by TEM, DLS, MALLS, and SAXS, with mean diameters ranging from 35 to 100 nm. The latter technique was particularly informative: data fits to a spherical micelle model enabled calculation of the core diameter, surface area occupied per copolymer chain, and the mean aggregation number (Nagg). The scaling exponent derived from a double-logarithmic plot of core diameter vs PBzMA DP suggests that the conformation of the PBzMA chains is intermediate between the collapsed and fully extended state. This is in good agreement with 1H NMR studies, which suggest that only 5−13% of the BzMA residues of the core-forming chains are solvated. The Nagg values calculated from SAXS and MALLS are in good agreement and scale approximately linearly with PBzMA DP. This suggests that spherical micelles grow in size not only as a result of the increase in copolymer molecular weight during the PISA synthesis but also by exchange of individual copolymer chains between micelles and/or by sphere–sphere fusion events.

Journal Keywords: RAFT polymerization; Copolymerization; Nanoparticles; Copolymers; Colloids

Subject Areas: Chemistry, Materials

Instruments: I22-Small angle scattering & Diffraction

Added On: 08/02/2016 15:03


Discipline Tags:

Soft condensed matter physics Chemistry Materials Science Organic Chemistry Nanoscience/Nanotechnology Polymer Science

Technical Tags:

Scattering Small Angle X-ray Scattering (SAXS)