Simultaneous reverse and normal initiation of ATRP

Details Simultaneous reverse and normal initiation of ATRP Simultaneous reverse and normal initiation of ATRP

2002-10-15

2004-07-06

Cheung, William (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S091000, C526S227000, C526S206000, C526S236000, C526S219600

Reexamination Certificate

active

06759491

ABSTRACT:

FIELD OF THE INVENTION
The present invention is directed to polymerization processes and more directly related to an initiation system for controlled radical polymerization processes.
DESCRIPTION OF THE INVENTION
ATRP is one of the most successful controlled/“living” radical processes (CRP) developed and has been thoroughly described in a series of co-assigned U.S. Patents and Applications, U.S. Pat. Nos. 5,763,546; 5,807,937; 5,789,487; 5,945,491; 6,111,022; 6,121,371; 6,124,411; 6,162,882; 6,407,187; and U.S. patent application Ser. Nos. 09/018,554; 09/359,359; 09/359,591; 09/369,157; 09/534,827; 09/972,046; 09/972,056; 09/972,260; 10/034,908; and 10/098,052 all of which are herein incorporated by reference, and has been discussed in numerous publications by Matyjaszewski as co-author and reviewed in several publications.
A living polymerization process is a chain growth process without or with an insignificant amount of chain breaking reactions, such as transfer and termination reactions. Controlled/living polymerization, herein “controlled polymerization”, is a chain growth process that under controlled polymerization conditions provides effective control over the chain growth process to enable synthesis of polymers with molecular weight control and narrow polydispersities or molecular weight distributions. Molecular weight control is provided by a process having a substantially linear growth in molecular weight of the polymer with monomer conversion accompanied by essentially linear semilogarithmic kinetic plots, in spite of any occurring terminations. Polymers from controlled polymerization processes typically have molecular weight distributions, characterized by the polydispersity index (“PDI”), of less than or equal to 2. The PDI is defined by the ratio of the weight average molecular weight to the number average molecular weight, M
w
/M
n
. More preferably in certain applications, polymers produced by controlled polymerization processes have a PDI of less than 1.5, and in certain embodiments, a PDI of less than 1.3 may be achieved.
Polymerization processes performed under controlled polymerizations conditions achieve these properties by consuming the initiator early in the polymerization process and, in at least one embodiment of controlled polymerization, an exchange between an active growing chain and dormant polymer chain is equivalent to or faster than the propagation of the polymer. A controlled radical polymerization (“CRP”) process is a process performed under controlled polymerization conditions with a chain growth process by a radical mechanism, such as, but not limited to, atom transfer radical polymerization, stable free radical polymerization, specifically, nitroxide mediated polymerization, reversible addition-fragmentation transfer/degenerative transfer/catalytic chain transfer radical systems. A feature of controlled radical polymerizations is the existence of an equilibrium between active and dormant species. The exchange between the active and dormant species provides a slow chain growth relative to conventional radical polymerization, but all polymer chains grow at the same rate. Typically, the concentration of radicals is maintained low enough to minimize termination reactions. This exchange, under appropriate conditions, also allows the quantitative initiation early in the process necessary for synthesizing polymers with special architecture and functionality. CRP processes may not eliminate the chain breaking reactions, however, the chain breaking reactions are significantly reduced from conventional polymerization processes.
Polymers produced under controlled polymerization conditions have a degree of polymerization that may be determined from the ratio of the amount of consumed monomer to the initiator, a polydispersity close to a Poisson distribution and functionalized chain ends. The level of control attained in a particular polymerization process is typically monitored by analyzing the kinetics of the polymerizations, the evolution of molecular weights, polydispersities and functionalities with conversion.
The equilibrium required for ATRP controlled polymerization processes has been attained using two different initiation methods or activation reactions called respectively, normal and reverse ATRP. See, for example, U.S. Pat. No. 5,763,548.
Unless otherwise indicated, all numbers expressing quantities of ingredients, time, temperatures, and so forth used in the present specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, may inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
Normal ATRP Initiation
Normal ATRP processes are initiated by the redox reaction between a initiator comprising a transferable atom or group and catalyst comprising a transition metal complex in a lower oxidation state. A redox reaction occurs between the initiator and the transition metal complex. The transferable atom or group is a group that may be homolytically cleaved from an initiator by the catalyst, thereby oxidizing the catalyst to a higher oxidation state and forming a radical thereby activating the initiator residue for monomer addition. After initiation, an ATRP process, generally, is based a dynamic equilibrium between a transition metal complex reversibly activating and deactivating the polymer chain via a similar homolytic atom or group transfer via a redox reaction. Subsequent to monomer addition, the polymer chain is activated by the removal of a transferable atom or group from the end of the polymer chain and may then deactivated by return of a transferable atom or group in the reverse reaction, the returning atom or group may not necessarily be the same atom or group removed in the activating step or even from the same transition metal complex. The equilibrium between the growing and dormant chains allows the synthesis of well-defined polymers with complex architecture. During the dynamic equilibrium the transition metal complex cycles between a lower oxidation state and a higher oxidation state. The advantages of normal initiation of ATRP include that the initiator includes the transferable atom or group needed to terminate each polymer chain, therefore no additional transferable atoms or groups are required to be added by other components of the polymerization process in order to attain polymers with the desired degree of polymerization at high conversion of monomer(s) to polymer. Therefore, only enough transition metal complex in the lower oxidation state is needed to provide suitable catalytic activity to the process. By suitable catalytic activity, it is meant that the polymerization comprises an amount of catalyst needed to drive the reaction to a desired degree of polymerization in a time that allows appropriate heat control to allow for a controlled reaction. The disadvantages of normal initiation of ATRP are that the transition metal complex in the lower oxidation state is less stable than the transition metal complex in the higher oxidation state and, typically without special handling procedures, has to be prepared at the time of reaction or stored under an inert atmosphere. Further, care has to be taken with the other reagents in the reaction to reduce the

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