Controlled free‐radical polymerization has been monitored with great interest in recent years since it offers an opportunity to combine the advantages of conventional free‐radical polymerization with those of living ionic polymerization. We present the 1,1‐diphenylethene (DPE) method which enables us to produce block copolymers on an industrial scale by a free‐radical mechanism.
This DPE process enables industrially relevant monomers, such as styrene, methacrylates, acrylates, methacrylic acid, acrylic acid and N‐vinyl compounds, to be converted into block copolymers. The synthesis can be carried out in organic solvents, without solvents or in water.
We have been able to demonstrate, that the addition of 1,1‐diphenylethylene to a normal free‐radical polymerization results in polymers whose molar mass, after a short uncontrolled phase, increases in a linear manner with conversion. The amount of 1,1‐diphenylethylene added also determines the order of magnitude of the final molar mass. It was also possible to employ the polymers isolated during this polymerization as initiators for the polymerization of a further monomer, resulting in the formation of block copolymers.
With possibly somewhat reduced claims on the perfection of the structures, a wide variety of possibilities arise with the known advantages of free‐radical polymerization.
The one‐pot synthesis is carried out by simple successive addition of the desired monomers and has already been used successfully on an industrially relevant scale.
The synthesis and characterization of poly(styrene-g-ferrocenyldimethylsilane), the first
organic−organometallic graft copolymer, are reported. This was permitted by the discovery that 1,1-diphenylethylene (DPE) can effectively cap the living anionic polyferrocenylsilane generated by the ring-opening polymerization (ROP) of the dimethyl-substituted [1]ferrocenophane 1 using n-BuLi as the
initiator. The resultant living DPE-capped polymer was then reacted with the chloromethyl functionalities
of poly(styrene-co-chloromethylstyrene) (PS-co-PCMS) (3) to afford the polystyrene−polyferrocenylsilane
graft copolymers 5a and 5b. These graft copolymers were then analyzed using differential scanning
calorimetry and wide-angle X-ray scattering which indicated that the materials are essentially amorphous,
with at most a very low degree of crystallinity. Cyclic voltammetry of 5b in CH2Cl2 showed a well-resolved
wave voltammogram with a redox coupling ΔE of ca. 0.23 V, characteristic of the presence of significant
Fe- - -Fe interactions in the grafted organometallic side chains. Polymer 5b was also characterized by
thermogravimetric analysis which indicated that the material is thermally stable to weight loss up to ca.
300 °C.
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