Standard Reference Material 2881 - National Institute of Standards ...

1. IntroductionThe certification of the absolute molecular mass distribution (MMD) of an n-octyl-initiated,proton-terminated, low mass, atactic polystyrene (PS) by matrix-assisted laser desorptionionization time-of-flight mass spectrometry (MALDI-TOF MS) is fully described. This polymerhas been designated Standard Reference Material (SRM) 2881. The material constituting SRM2881 was prepared commercially for the NIST Polymers Division specifically for use as anarrow-distribution polymer standard. Anticipated uses include calibration of massspectrometers and size exclusion chromatographs (SEC) in accordance with various internationalstandards (described below), as well as any other application where quantitative knowledge ofthe entire MMD is necessary. The work described here, and in related references, provides ameans to create absolute molecular mass distribution standards of any low mass, narrowpolydispersity polymer including proprietary materials.This work is the culmination of a multi-year effort that required development of newmethods in sample preparation 1 , numerical instrument optimization 2 , and unbiased dataanalysis 3-5 . This report mainly covers the final uncertainty determination and discusses aTaylor’s expansion methodology to certify the absolute MMD of polydisperse samples.2. Preparation, Initial Characterization, and Bottling2.1 SynthesisThe polystyrene used for this SRM was prepared commercially by Scientific PolymerProducts, Inc. (Ontario, NY) by anionic polymerization of styrene initiated with n-octyl lithium(FMC Lithium, Gastonia, NC) and terminated with a proton. From the preparation chemistry, weexpected the polymer to be atactic polystyrene of the form:CH 3 -(CH 2 ) 7 -[CH 2 -CHPh] n -CH 2 -CH 2 -Ph [2.1]where Ph refers to the pendant phenyl group. The material was received in the form of a clean,white powder.4