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

Journal Article · Tue Sep 29 00:00:00 EDT 2015 · Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics

DOI:https://doi.org/10.1103/PhysRevE.92.030302· OSTI ID:1265870

Hyatt, John S. ^[1]; Do, Changwoo ^[2]; Hu, Xiaobo ^[1]; Choi, Hong Sung ^[3]; Kim, Jin Woong ^[4]; Lyon, L. Andrew ^[1]; Fernandez-Nieves, Alberto ^[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)

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.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC05-00OR22725; 50603-DNI7
• OSTI ID: 1265870
• Alternate ID(s): OSTI ID: 1222430
• Journal Information: Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics, Vol. 92, Issue 3; ISSN 1539-3755
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE