Usage: Polyguanidine’s high water solubility, antimicrobial activity, biocide efﬁciency and nontoxicity, make it favourable as a broad-spectrum disinfectant in the medical, fiber, textile and plastic industries. This polymer especially promising as it eliminates disadvantages associated with the majority of existing disinfecting products, the most prominent being toxicity, unpleasant odor and low effectiveness. Structure and MW of the guanidine polymer can be characterized using GPC to determine the wet strength and antimicrobial activity of the polyguanidine end product.
Manufacturing: Polyguanidine can be obtained by modifying a polycarbodiimide with an amine or through polycondensation of hexamethylenediamine with a guanidine in addition to using hydrazine hydrate during the condensation polymerization process.
Chemical Formula: CH5N3
Figure 1. Structure of a single guanidine monomer
Two polyguanidine samples were dissolved in dimethyl sulfoxide (DMSO) / Water (85/15 v/v) in addition to 0.1M lithium bromide (LiBr) and 0.02M phosphoric acid (H3PO4) at a concentration of 10 mg/mL and left to dissolve for 2 hours before filtering through 0.22µm nylon filters. Sodium nitrate is used to eliminate ionic interaction between the columns and samples. Analysis was completed on a Viscotek Triple Detector Array (TDA) 302 equipped with a Refractive Index (RI) detector, Viscometer, Right Angle (90o) Light Scattering (RALS) and Low Angle (7o) Light Scattering (LALS). Separation was performed using two PolyAnalytik AquaGelTM mixed bed columns (2 x PAA 206M) connected in series. Samples were injected at a volume of 100 µL and eluted through the system at flow rate of 0.75 mL/min in DMSO/Water (85/15 v/v) + 0.1M LiBr + 0.02M H3PO4. A temperature of 70oC was maintained during separation and detection.
Triple detection analysis provides absolute MW, hydrodynamic size, intrinsic viscosity and concentration. An overlaid multi-detector chromatogram for a polyguanidine sample can be seen in Figure 2. Using data from RI, light scattering and the viscometer, the absolute molecular weight and radius of hydration were determined and reported as an average from 3 injections, see Table 1. Triple detection method allows for good repeatability of injections as can be seen from the %RSD less than one.
Figure 2. A typical multi detector overlay of chromatograms for a sample of polyguanidine
Table 1. Table 1. Molecular weight and size of a polyguanidine sample derived from triple detection method
Characterization of the polyguanidine samples was successfully achieved using a multi-detector GPC. Two samples were analyzed and absolute MW and the radius of hydration were determined and both had a % RSD less than one percent indicating reproducibility. This method allows for analysis of structurally complex as well as common types of polymers providing accurate and precise values for absolute Mw and size which are essential for quality control of commercial products.