Studies on the Radical Polymerization of Methyl Methacrylate in Bulk and in Benzene Using Totally Deuterated Monomer Technique

Abstract

Totally deuterated methyl methacrylate (MMA-d8) was polymerized with AIBN in bulk at 60°C, and the resultant polymer was analyzed for the initiator fragment by 1 H NMR spectroscopy. Amount of the AIBN fragment at the beginning of the chain was found to be 1.15 per molecule, indicating 85% of the polymer molecules formed through disproportionation reaction. NMR analysis of the undeuterated PMMA prepared under the same conditions showed that the polymer contained 0.36 vinylidene double bond at the chain end. This is consistent with the results obtained from the P (MMA-d8). P (MMA-d8) prepared with BPO in benzene at 60°C had 1.20 initiator fragment per chain, 82% of which was phenyl group and 18% benzoyloxy one.

Assigned Cotactic Parameters in the Radical Copolymerization of Methyl Methacrylate with Various Methacrylates

“…In both spectra, the isotactic and heterotactic oc-CH 3 signals were overlapped with peaks for the initiator fragment, (CH 3 ) 2 C(CN)-. 22 The spin-lattice relaxation time (T 1 ) of the latter signals (l.Os) was longer enough than those for oc-CH 3 protons (0.25-0.3 s) so that the peaks could be eliminated in the partially relaxed spectra (Figures l(B) and 2(B)) taken at an optimized pulse interval between 180° and 90° pulses as described in the figure captions. On the other hand, the residual protons in the oc-methyl group ofMMAd8 unit also overlapped with the CH 3 signals of MMA unit derived from M 2 units.…”

“…For the copolymerization systems, excluding that of PPyTMA, the tacticity for M2 centered triad, i.e., M 1 M 2 M 1 , M 1 M 2 M 2 , M 2 M 2 M 1 , and M 2 M 2 M 2 , was calculated with ------------------------ 22 derived from the tacticity of the homopolymers is not enough to describe the configurational sequence in the strict sense, because stereoregularity of homopolymers of triarylmethyl methacrylates apparently do not obey Bernoullian statistics. Nevertheless, the average values calculated were very close to the observed ones.…”

Characterization of Polymerization Reagents Incorporated into Poly(methyl methacrylate) Chains by Pyrolysis-Gas Chromatography

“…1 -4 In some cases, NMR has been successfully applied to characterize the chain ends of relatively low molecular weight oligomers 1 and the polymers prepared with isotope-labelled reagents such as 13 C enriched initiatorsl.2 and perdeuterated monomers. 3 The NMR methods often provide significant information not only on the number of initiator fragments but also how the fragment is incorporated into the polymer chain. 3 · 4 On the other hand, pyrolysis-gas chromatography (PyGC) is a simple but extremely sensitive technique which often provides unique structural supplemental information to that obtained by conventional spectroscopic methods.5·6 Particularly, the recent advent of extremely efficient fused-silica capillary columns has greatly improved the resolution and extended the applicability of PyGC to characterizing the microstructures of polymers such as branching in polyethylenes, 7 disordered configuration in highly alternating copolymers, 8 junctions of different monomer units in tapered copolymers, 9 and networks in vulcanized rubbers.…”

Effect of NMR Signal from Initiator Fragment on Triad Tacticities of Poly(methyl methacrylate)s Formed by 2,2′-Azobisisobutyronitrile and Benzoyl Peroxide

“…The assignment of the initiator fragment signals was confirmed by comparing the spectrum with that of poly(methyl methacrylate-d 8 ) prepared by AIBN and also with the spectrum of PMMA by AIBN"d 12 . 5 The triad tacticity of AIBN-polymerized PMMA was determined from the 500 MHz NMR spectrum by omitting the contribution of the initiator fragment signals. The corrected tacticity values thus obtained were slightly lowered in isotactic and heterotactic triads while increased in syndiotactic triad as compared with the data from the 100 MHz spectrum (Table II).…”

“…The corrected tacticity is very close to the tacticity of PMMA prepared by BPO, which is independent of the NMR frequencies (Table II). When the degree of polymerization of PMMA exceeds 1000, the contribution of AIBN fragment signals can be 1128 neglected since the number of the initiator fragment in a polymer chain is about unity 5 and the relative fraction becomes negligibly small.…”