Open AccessSegregation of mass at the periphery ofN
Author(s) -
John S. Hyatt,
Changwoo Do,
Xiaobo Hu,
Hong Sung Choi,
Jinwoong Kim,
L. Andrew Lyon,
Alberto FernándezNieves
Publication year - 2015
Publication title -
physical review. e, statistical, nonlinear and soft matter physics
Language(s) - English
Resource type - Journals
eISSN - 1550-2376
pISSN - 1539-3755
DOI - 10.1103/physreve.92.030302
Subject(s) - radius of gyration , hydrodynamic radius , acrylic acid , poly(n isopropylacrylamide) , radius , molar mass , dynamic light scattering , polymer , materials science , particle (ecology) , thermodynamics , statistical physics , chemical physics , physics , nanoparticle , nanotechnology , copolymer , computer science , composite material , computer security , oceanography , geology
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. Specifically, 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. 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.Research conducted at ORNL's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. Funding was provided by the ACS Petroleum Research Fund (Grant No. 50603-DNI7), the IBB seed grant, the research partnership between Children's Healthcare of Atlanta and the Georgia Institute of Technology, and Shinsegae International Company