Block polymer systems containing spatially separated positive and negative charges are desirable for a number of applications, including biomedical devices, membrane separations, and coatings. Unfortunately, the tendency of positive and negative block polymers to charge cancel and form an insoluble coacervate precipitate leads to processing difficulties in the fabrication of charged thin films. We use postpolymerization modifications to simultaneously add both negative and positive charges to self-assembled neutral ABC triblock polymer thin films. Using reversible addition-fragmentation chain transfer polymerization, we synthesized triblock terpolymers consisting of poly(n-propyl styrene sulfonic ester), poly(4-chlorostyrene), and poly(vinylbenzyl chloride). The chemical functionalization of both charged blocks was accomplished simultaneously through exposure to gaseous trimethylamine in a single step at room temperature, simplifying the synthetic procedure and preserving the microstructure of the thin film. The quantitative functionalization was tracked through attenuated total reflectance infrared spectroscopy, and the thin film morphology was evaluated using intermodulation atomic force microscopy, transmission electron microscopy, and grazing-incidence small-angle X-ray scattering.
Bibliographical noteFunding Information:
This work was supported by the National Science Foundation under DMR-1609459 and in part under DMR-1725272. M.R.R. held the Camille and Henry Dreyfus Foundation Postdoctoral Fellowship in Environmental Chemistry while performing this work.
Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from the National Science Foundation (NSF) through the MRSEC program. The authors would like to acknowledge Greg Haugstad of the Characterization Facility, who contributed to the data collection methods involving intermodulation atomic force microscopy. Portions of this work were conducted in the Minnesota Nano Center, which is supported by the NSF through the National Nano Coordinated Infrastructure Network, Award Number NNCI-1542202. This research used resources of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The GISAXS data were obtained at the 8-ID-E beamline and analyzed by GIXSGUI software provided by the APS user facility.
Copyright © 2020 American Chemical Society.
- atomic force microscopy
- block polymers
- postpolymerization modification
- thin film