The invention relates to a method of forming carbon monoxide-containing polymers from multi-component syngas feeds and at least one vinyl comonomer. Feeds useful in the practice of the invention comprise ethylene in an amount ranging from about 5 to about 40 mole %, carbon monoxide is an amount ranging from about 1 to about 40 mole %, hydrogen in an amount ranging from about 4 to about 55 mole %, carbon dioxide in an amount ranging from about 3 to about 10 mole %, and methane in an amount ranging from about 4 to about 85 mole %. The feed may also include acetylene in an amount ranging up to about 10 mole %. The feed may contain at least one free radical-polymerizable vinyl comonomer, or a cofeed containing such a comonomer can be used.