Polymer Surfactant Molecular Weight By Maldi Mass Spectrometry

Matrix-assisted laser desorptionlionization time-of-flight mass spectrometry (MALDI-TOF MS) is a useful tool to determine the molecular weight of synthetic polymers, but the accuracy and repeatability of this method is still unclear. In thisthesis, the determination of molecular weight and molecular weight distribution of polyelectrolytes, poly (acrylic acid), poly (styrene sulfonic acid) and nonylphenol ethoxylate were achieved by MALDI-TOF MS.Sodium forms of poly(acrylic acid) and poly(styrene sulfonic acid) are prepared in the acid forms with ion-exchange resin as the metallic ion in the sample will made the spectrum too complicated to distinguish the polymer with different monomer.In this thesis, the experiment techniques were sysmetically studies especially for the determination of matrix and matrix conce*ration. It is found that sinapinic acid were successfully used in the molecular determination of poiy (acrylic acid) by MALDL'TOF with the detection mode of negative ion. A new matrix (nor-harmane) was used in the determination of poly (styrene sulfonic acid) with the negativeionMALDI-TOF MS. After the addition of excess of K4- or Na ions in the nonylphenolethoxylate, the molecular peaks in the spectrum of [M+ K]4- or [M± Na]4- adducts are much stronger than others so that the spectrum become very clear.The quantitative determination of MALDI-TOF MS for the molecular weight dispersities of poly (acrylic acid), poly (styrene sulfonic acid), nonylphenol ethoxylate surfactants are also discussed.