(180o) Complete Molecular Weight Distributions of Linear Polymers Using Electrospray Differential Mobility Analysis

Molecular weight measurements play a key role in determining the structure-property relationships and the utility of polymers for a broad array of applications.  However, most scientifically and commercially interesting polymers are at least marginally polydispersed, which requires the use of multiple instruments to determine metrics of the length distribution.  These include GPC/SEC for weight-average molecular weight (M_w), osmotic pressure for number-average molecular weight (M_n), and so forth.  Here we report on a new technique to determine the complete polymer molecular weight distribution from 1 kDa to 75 GDa at high resolution (~ 0.3 kDa).  This technique, electrospray differential mobility analysis (ES-DMA), allows all metrics of the molecular weight distribution including M_w, M_n, and the polydispersity index (PDI) to be simultaneously measured using a single instrument in less than an hour. This technique is particularly advantageous for characterizing highly-charged polymers.  Previous ES-DMA efforts have found the size of monodispersed polymer strands to be proportional to their molecular mass to the 1/3 power for water soluble, water insoluble, and biopolymers such as DNA.  Our work highlights the experimental discovery of a new scaling regime where the polymer size is proportional to the molecular mass to the ½ power and its consequences for determining the full multimodal molecular weight distributions of polymers.