1989 Fiscal Year Final Research Report Summary
Development of Living Cationic Polymerization: Novel Methods for Controlled Polymer Synthesis
| Project/Area Number |
63470099
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
高分子合成
|
|---|
| Research Institution | KYOTO UNIVERSITY |
|---|
Principal Investigator |
HIGASHIMURA Toshinobu Kyoto University Professor, 工学部, 教授 (20025860)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
SAWAMOTO Mitsuo Kyoto University Research Instructor, 工学部, 助手 (90150325)
|
|---|
| Project Period (FY) |
1988 – 1989
|
| Keywords | Cationic Polymerization / Living Polymerization / Initiator / Carbocation / Living Polymer / Block Copolymer / Vinyl Ether / Styrene Derivative |
|---|
| Research Abstract |
This research project was directed toward three objectives: (a) to establish general principles of living cationic polymerization; (b) to develop new initiating systems for high-temperature living cationic processes; and (c) to expand the scope of living cationic polymerization to a variety of monomers.
(a) General Principles of Living Cationic Polyrarization. Living cationic polymerization has been difficult because of the iherent instability of the carbocationic intermediate therein. We theorized that "nucleophilic stabilization" of the unstable growing carbocation might lead to living pationic polymerization. On the basis of this hypothesis, we have proposed two methods to stabilize the growing carbocations; (A) stabilization by a suitably nucleophilic counteranion; and (B) stabilization by a added weak Lewis base. Both principles have been shown valid and thus led to a variety of new initiating systems.
(b) High-Temperature Living Cationic Polymerization in the Presence of Added Base
… More
s. In general, strongly acidic metal halides (like EtAlCl_2) cannot induce living cationic polymerization, because they generate counteranions too weakly nucleophilic to stabilize the growing carbocations. Our principle (B) turned out specifically effective for these systems; and addition of such weak Lewis bases as esters, ethers, and pyridine derivatives was found to stabilize the growing cation through nuclephilic interaction and thereby allows living cationic polymerization of vinyl ethers at temperatures as high as +70 ﾟC.
(c) Living Cationic Polyrarization of Styrene Derivatives. With use of the hydrogen iodide/zinc iodide (HI/ZnI_2) initiating system, which is based on our principle (A), living cationic polymerization has been achieved not only for vinyl ethers but also for styrene derivatives. Specifically, well-defined living polymers were obtained from p-t-butoxystyrene even at room temperature, though it carries an acid-sensitive alkoxyl group. Hydrolysis of the polymer led to poly(p-vinylphenol) of a controlled molecular weight. Block copolymers of p-t-butoxystyrene with various vinyl monomers were also synthesized. Less
|
