1.3. Scope of Review 5161 2. Methacrylate Polymerization 5161 2.1. Lanthanide Complexes 5161 2.1.1. Nonbridged Lanthanocenes 5161 2.1.2. ansa-Lanthanocenes 5164 2.1.3. Half-Lanthanocenes 5166 2.1.4. Non-lanthanocenes 5166 2.2. Group 4 Metallocenes 5170 2.2.1. Nonbridged Catalysts 5170 2.2.2. ansa-C2v-Ligated Catalysts 5173 2.2.3. ansa-C2-Ligated Catalysts 5173 2.2.4. ansa-C1-Ligated Catalysts 5176 2.2.5. ansa-Cs-Ligated Catalysts 5177 2.2.6. Constrained Geometry Catalysts 5178 2.2.7. Half-Metallocene Catalysts 5180 2.2.8. Supported Catalysts 5180 2.3. Other Metallocene Catalysts 5180 2.4. Nonmetallocene Catalysts 5181 2.4.1. Group 1 and 2 Catalysts 5181 2.4.2. Group 13 Catalysts 5183 2.4.3. Group 14 Catalysts 5186 2.4.4. Transition-Metal Catalysts 5187 3. Acrylate Polymerization 5188 3.1. Lanthanocenes 5188 3.2. Group 4 Metallocenes 5189 3.3. Nonmetallocenes 5190 4. Acrylamide and Methacrylamide Polymerization 5191 4.1. Acrylamides 5191 4.2. Methacrylamides 5192 4.3. Asymmetric Polymerization 5193 5. Acrylonitrile and Vinyl Ketone Polymerization 5196 5.1. Acrylonitrile 5196 5.2. Vinyl Ketones 5196 6. Copolymerization 5197 6.1. Polar-Nonpolar Block Copolymers 5197 6.2. Polar-Nonpolar Random Copolymers 5199 6.3. Polar-Polar Copolymers 5204 7. Ion-Pairing Polymerization 5206 8. Summary and Outlook 5208 9. Acknowledgments 5208 10. References 5208

Coordination polymerization of polar vinyl monomers by single-site metal catalysts.

3.3.3. Ionic Bonding or Interaction 5141 3.3.4. Multiple Hydrogen Bonding Interactions 5142 4. Stereospecific Living Radical Polymerization 5143 4.1. Acrylamides and Methacrylamides 5143 4.2. Methacrylates and Acrylates 5146 4.3. Vinyl Esters, Vinyl Amides, and Vinyl Chloride 5148 4.4. Stereoblock and Stereogradient Polymers 5149 4.4.1. Stereoblock Polymers 5149 4.4.2. Stereogradient Polymers 5151 5. Conclusions 5151 6. Acknowledgments 5152 7. References 5152

Stereospecific living radical polymerization: dual control of chain length and tacticity for precision polymer synthesis.

Anionic vinyl polymerization—50 years after Michael Szwarc

Stereoregular polymerization of α-substituted acrylates

Highly isotactic PMMAs with narrow molecular weight distribution (Mw/Mn<1.2) have been prepared by the polymerization of MMA in toluene at −78°C initiated by t-C4H9MgBr prepared in diethyl ether. The polymerization proceeded in a “living” manner, in which the initiation reaction was fast and quantitative whereas the propagation was slow. The ether solution of t-C4H9MgBr used as the initiator contained almost equal amounts of MgBr2 produced by an Wurtz type coupling during the preparation. It has been found from 1H NMR analyses that the excess amount of MgBr2 contributes to form the initiating species of homogeneous activity and stereospecificity. Polymerizations of MMA by n-, iso-, and s-C4H9MgBr were also investigated in toluene at −78°C. With an increase in the bulkiness of the alkyl group the isotacticity of the polymer increased and the molecular weight distribution became narrower. The addition of MgBr2 also increased the isotacticity of the polymer. The results of block copolymerizations of MMA and MMA-d8 or ethyl methacrylate are also described.

/pdf/living-and-highly-isotactic-polymerization-of-methyl-4ud7w9aswy.pdf

Living and Highly Isotactic Polymerization of Methyl Methacrylate by t-C4H9MgBr in Toluene

In order to determine the stereoregularity of poly(4-vinylpyridine), 4-vinylpyridine-β,β-d2 was synthesized from 4-acetylpyridine. The 1H-NMR spectra of the deuterated and nondeuterated polymers were measured and analyzed. From the 1H-NMR spectra of poly(4-vinylpyridine-β,β-d2), triad tacticity can be obtained, while the 1H-NMR spectra of nondeuterated poly(4-vinylpyridine) give the fraction of isotactic triad. The 13C-NMR spectra of poly(4-vinylpyridine) were also observed, and the spectra of C4 carbon of polymers were assigned by the pentad tacticities. The fraction of isotactic triad of poly(2-vinylpyridine) and poly(4-vinylpyridine) obtained under various polymerization conditions were determined. The radical polymerization and anionic polymerizations with phenylmagnesium bromide and n-butyllithium as catalysts of 4-vinylpyridine gave atactic polymers.

Stereoregularity of poly(2-vinylpyridine) and poly-(4-vinylpyridine)

13C nuclear magnetic resonance spectra of polyacrylates and their model compounds

In order to know the effect of the steric structure of the ester groups on the stereoregularity of polymers, several methacrylic esters were radically and anionically polymerized. From the determination of the stereoregularity of the poly(methacrylates) by NMR, it was concluded that with decreasing steric factor of the ester groups the syndiotacticity of radically polymerized polymers decreases and also the isotacticity of the polymers obtained with phenylmagnesium bromide as catalyst at room temperature decreases.



Um die Wirkung der sterischen Struktur der Estergruppen auf die Stereoregularitat von Polymeren kennenzulernen, wurden verschiedene Methacrylsaureester radikalisch und anionisch polymerisiert. Aus der Bestimmung der Stereoregularitat der Poly(methacrylate) durch NMR wurde geschlossen, das mit abnehmendem sterischem Faktor der Estergruppen die Syndiotaktizitat von radikalisch polymerisierten Polymeren abnimmt und die Isotaktizitat von Polymeren, die mit Phenylmagnesiumbromid als Katalysator bei Raumtemperatur erhalten werden, ebenfalls abnimmt.

The microtacticity of poly(acrylic esters)

The stereoregularity and molecular weight distribution of poly(methylmethacrylate)s prepared with phenylmagnesium bromide or diphenylmagnesium as catalyst in tetrahydrofuran/toluene mixed solvents were investigated in detail. Some of the polymers were fractionated according to molecular weight or by adsorption with silical gel and the stereoregularities of the fractions were determined. An eneidic mechanism of propropagation was proposed based on the experimental results.



1H NMR spectroscopy of deuterated phenylmagnesium bromide and of its reaction with methyl methacrylate indicated that an eneidic mechanism resulted from a Schlenk type equilibrium, which is shifted to the diphenylmagnesium species at low temperatures and in nonpolar solvents.

Polymerization of methyl methacrylate with phenylmagnesium bromide — stereoregularity, molecular weight distribution and polymerization mechanism —

In order to determine the stereoregularity of poly(2-vinylpyridine), 2-vinylpyridine-..beta..,..beta..-d/sub 2/ was synthesized. The /sup 1/H-NMR spectra of the deuterated polymer in D/sub 2/SO/sub 4/ and o-dichlorobenzene solutions showed three peaks, which were assigned to triad tacticities. Since the absorptions of heterotactic and syndiotactic triads of methine protons overlap those of methylene protons in nondeuterated polymers, only isotactic triad intensities can be obtained from the /sup 1/H-NMR spectra of nondeuterated poly(2-vinylpyridine). The /sup 13/C-NMR spectra of poly(2-vinylpyridine) were obtained in methanol and sulfuric acid solutions. In methanol solution the absorption was split into three groups, which cannot be explained by triads, and in sulfuric acid solution several peaks were observed. These splittings may be due to pentad tacticity. The results show that poly(2-vinylpyridine) obtained by radical polymerization is an atactic polymer.

Taiichi Kanai

Papers

Stereoregularity of poly(2-vinylpyridine) and poly-(4-vinylpyridine)

13C nuclear magnetic resonance spectra of polyacrylates and their model compounds

The microtacticity of poly(acrylic esters)

Polymerization of methyl methacrylate with phenylmagnesium bromide — stereoregularity, molecular weight distribution and polymerization mechanism —

Stereoregularity of poly(2‐vinylpyridine) determined by 1H‐NMR and 13C‐NMR spectroscopy