Evaluation of an atomic force microscopy pull-off method for measuring molecular weight and polydispersity of polymer brushes: effect of grafting density

Langmuir : the ACS Journal of Surfaces and Colloids
Diane GoodmanDonald E Brooks

Abstract

The accuracy of the molecular weights Mn and polydispersities of polymer brushes, determined by stretching the grafted chains using atomic force microscopy (AFM) and measuring the contour length distribution, was evaluated as a function of grafting density sigma. Poly(N,N-dimethylacrylamide) brushes were prepared by surface initiated atom transfer radical polymerization on latex particles with sigma ranging between 0.17 and 0.0059 chains/nm2 and constant Mn. The polymer, which could be cleaved from the grafting surface by hydrolysis and characterized by gel permeation chromatography (GPC), had a Mn of 30,600 and polydispersity (PDI) of 1.35. The Mn determined by the AFM technique for the higher density brushes agreed quite well with the GPC results but was significantly underestimated for the lower sigma. At high grafting density in good solvent, the extended structure of the brush increases the probability of forming segment-tip contacts located at the chain end. When the distance between chains approached twice the radius of gyration of the polymer, the transition from brush to mushroom structure presumably enabled the formation of a larger number of segment-tip contacts having separations smaller than the contour length, whi...Continue Reading

References

Sep 4, 1989·Physical Review Letters·M Murat, G S Grest
Apr 20, 2005·Langmuir : the ACS Journal of Surfaces and Colloids·Diane GoodmanDonald E Brooks

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Citations

Apr 20, 2012·ACS Applied Materials & Interfaces·Bryan R CoadLaurence Meagher
Feb 21, 2008·Journal of Biomedical Materials Research. Part a·Alexander E IvanovBo Mattiasson
Oct 7, 2016·ACS Applied Materials & Interfaces·John J KeatingGeorges Belfort
Jan 26, 2018·Reports on Progress in Physics·A R Hall, M Geoghegan
Oct 10, 2012·Langmuir : the ACS Journal of Surfaces and Colloids·Shen ZhangHongwei Ma
Aug 2, 2017·Langmuir : the ACS Journal of Surfaces and Colloids·J P MahalikRajeev Kumar
May 2, 2020·Langmuir : the ACS Journal of Surfaces and Colloids·Chen XiaoSeong Han Kim

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