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Title: Segregation of mass at the periphery of N -isopropylacrylamide-co-acrylic-acid microgels at high temperatures

Here, we investigate poly(N-isopropylacrylamide) (pNIPAM) microgels randomly copolymerized with large mol % of protonated acrylic acid (AAc), finding that above the lower critical solution temperature the presence of the acid strongly disrupts pNIPAM's collapse, leading to unexpected new behavior at high temperatures. We see a dramatic increase in the ratio between the radius of gyration and the hydrodynamic radius above the theoretical value for homogeneous spheres, and a corresponding increase of the network length scale, which we attribute to the presence of a heterogeneous polymer distribution that forms due to frustration of pNIPAM's coil-to-globule transition by the AAc. Finally, we analyze this phenomenon using a Debye-Bueche-like scattering contribution as opposed to the Lorentzian term often used, interpreting the results in terms of mass segregation at the particle periphery.
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [4] ;  [1] ;  [1]
  1. Georgia Inst. of Technology, Atlanta, GA (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Shinsegae International, Seoul (South Korea)
  4. Hanyang Univ., Gyeonggi (South Korea)
Publication Date:
OSTI Identifier:
1265870
Grant/Contract Number:
AC05-00OR22725; 50603-DNI7
Type:
Accepted Manuscript
Journal Name:
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics (Print)
Additional Journal Information:
Journal Name: Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics (Print); Journal Volume: 92; Journal Issue: 3; Journal ID: ISSN 1539-3755
Publisher:
American Physical Society (APS)
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE