Molecular weights of natural rubbers from selected temperate zone plants

Abstract Molecular weights and molecular weight distributions are compared by gel permeation chromatography for rubbers from 33 north temperate zone plants, guayule, and Hevea. Rubbers isolated from all the northern plants had much lower weight‐average molecular weight ( M w ) values (9.72 × 10 4 –4.95 × 10 5 ) than milled Hevea (1.31 × 10 6 ) or guayule (1.28 × 10 6 ) rubber. Pycnanthemum incanum , Lamiastrum galeobdolon , Monarda fistulosa , and Vernonia fasciculata produced potentially useful natural rubbers having M w values above 4 × 10 5 and polydispersity factors of 3.1–4.5.