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Some peculiarities of the low-temperature polymerization of p-methylstyrene
Low-temperature polymerization of p-methylstyrene
1829
A n absolute method is here suggested, based on a combination of the "blind spot" principle a n d high-speed centrifuging. I t can be used to determine the differential compositional heterogeneity at the same time as the molecular weight distribution. I n a most convenient modification the method is applicable to copolymers where one of the components (I) possesses a chromophore which is absorptive in a certain section of the spectrum. Using the light absorption arrangement of [2] the sedimentation coefficient (c (s)) distribution can be determined for the first component alone (the second is n o t absorptive a n d therefore is invisible) (Fig. a). Then, in the same solvent and at exactly the same concentration, the total distribution of the copolymer is determined over s, qw(s), using a n y refractometric arrangement (Fig. b, solid line). I f the refractive index increments of the two components are known, a n d also the depth of the dish and optical constants of the ultracentrifuge, it is not hard to subtract the contribution of the first component from this curve (dashed line Fig. b). Separation of the contribution (Fig. c) gives the differential heterogeneity distribution. Despite its limitations, in this modification the method is highly convenient for studying theoretical problems of copolymerization. Besides this, it can be used to analyse the compositional heterogeneity of n a t u r a l a n d man-made [3] nucleoproteides. There are no limitations to the second modification of the method in which the solvent is varied b y using refractometric schemes of recording (one of the components "disappears" in a solvent having the same refractive index). But the procedure for processing the results is complicated because the sedimentation behaviour of the copolymers m a y be different in the two solvents. The experimental illustration a n d details of calculation will be dealt with in a report at present in progress. Translated by V. ALFORD
REFERENCES 1. S. Ya. FRENKEL', Vved. v statistich, teoriyu polimerizatsii. (Introduction to the Statistical Theory of Polymerization.) Izd. Nauka, Moscow-Leningrad, 1965; see also [2] 2. V. N. TSVETKOV, V. Ire. ESKIN a n d S. Ya. FRENKEL', Struktura makromol, v rastvorakh. (Structure of Macromoleeules in Solutions.) Izd. Nauka, Moscow, 1964 3. T. N. KOPYLOVA-SVIRIDOVA, I. A. KHODOSOVA, V. I. VOROB'YEV a n d S. Ya. FRENKEL', Dokl. Akad. Nauk SSSR 145: 1400, 1962
SOME PECULIARITIES OF THE LOW-TEMPERATURE POLYMERIZATION OF p-METHYLSTYRENE* N . D. PRISHCHEPA, YU. YA. GOL'D]~ARB a n d B . A. KREI~TSEL'
(Received 30 March 1966) IN AN I R spectral analysis of specimens of poly-p-methylstyrene (PMS) prepared b y lowtemperature polymerization over BFs-O(C2Hs) 2 in toluene a n d ethylchloride, the C]Ksgroup content was found to be higher t h a n normal. The lowering of the polymerization * Vysokomol. soyed. 8: No. 9, 1658-1659, 1966.
N . D . PRISHCHEPA et al.
1830
temperature had promoted an increase in CH2-group content. The variation was determined from the ratio of the optical densities of the methylene and phenyl group absorption bands. I n specimens produced at 0 ° in toluene, this ratio is 0"805, and at --78 ° D~86o/Dso2,: 1"935. For polymers prepared in ethylchloride at --50 and --130 °, D286o/Ds,~o is 0"935 and 3 respectively.
J t
f
f
8
8 /O-e
4
2
0
NMR spectra of specimens a a n d b. This increase in the methylene-group content of PMS was confirmed by NMR analysis. The Figure shows the NMR spectra of specimens a and b (D286o/Dso2o for specimen a was 0"805, and for specimen b, 1"5). The measurements were performed on an NMR spectrometer type 5535 working at a frequency of 40 Mc/s; the solvent was CCI~, the standard Si(CHs)4. I n the NMR spectrum ef specimen b the intensity of the peak with the chemical shift 1"2 v (CHI groups in the paraffin chain) had increased as compared with the corresponding peak in the spectrmn of specimen a. For the peak with the chemical shift 2"25 v (CHa groups combined in the benzene ring) the intensity had diminished. According to structural X-ray analysis PMS specimens containing the higher CH~ group content had a slightly crystalline structure. On the basis of the above data we suggest the following reaction for the formation of the polymer" ,~CH2--CH
~, -'-..,CH2--CH2
CH2
This can be regarded as a new example of polymerization with migration of the hydro. gen atom. Translated by V. ALFORD
1829
A n absolute method is here suggested, based on a combination of the "blind spot" principle a n d high-speed centrifuging. I t can be used to determine the differential compositional heterogeneity at the same time as the molecular weight distribution. I n a most convenient modification the method is applicable to copolymers where one of the components (I) possesses a chromophore which is absorptive in a certain section of the spectrum. Using the light absorption arrangement of [2] the sedimentation coefficient (c (s)) distribution can be determined for the first component alone (the second is n o t absorptive a n d therefore is invisible) (Fig. a). Then, in the same solvent and at exactly the same concentration, the total distribution of the copolymer is determined over s, qw(s), using a n y refractometric arrangement (Fig. b, solid line). I f the refractive index increments of the two components are known, a n d also the depth of the dish and optical constants of the ultracentrifuge, it is not hard to subtract the contribution of the first component from this curve (dashed line Fig. b). Separation of the contribution (Fig. c) gives the differential heterogeneity distribution. Despite its limitations, in this modification the method is highly convenient for studying theoretical problems of copolymerization. Besides this, it can be used to analyse the compositional heterogeneity of n a t u r a l a n d man-made [3] nucleoproteides. There are no limitations to the second modification of the method in which the solvent is varied b y using refractometric schemes of recording (one of the components "disappears" in a solvent having the same refractive index). But the procedure for processing the results is complicated because the sedimentation behaviour of the copolymers m a y be different in the two solvents. The experimental illustration a n d details of calculation will be dealt with in a report at present in progress. Translated by V. ALFORD
REFERENCES 1. S. Ya. FRENKEL', Vved. v statistich, teoriyu polimerizatsii. (Introduction to the Statistical Theory of Polymerization.) Izd. Nauka, Moscow-Leningrad, 1965; see also [2] 2. V. N. TSVETKOV, V. Ire. ESKIN a n d S. Ya. FRENKEL', Struktura makromol, v rastvorakh. (Structure of Macromoleeules in Solutions.) Izd. Nauka, Moscow, 1964 3. T. N. KOPYLOVA-SVIRIDOVA, I. A. KHODOSOVA, V. I. VOROB'YEV a n d S. Ya. FRENKEL', Dokl. Akad. Nauk SSSR 145: 1400, 1962
SOME PECULIARITIES OF THE LOW-TEMPERATURE POLYMERIZATION OF p-METHYLSTYRENE* N . D. PRISHCHEPA, YU. YA. GOL'D]~ARB a n d B . A. KREI~TSEL'
(Received 30 March 1966) IN AN I R spectral analysis of specimens of poly-p-methylstyrene (PMS) prepared b y lowtemperature polymerization over BFs-O(C2Hs) 2 in toluene a n d ethylchloride, the C]Ksgroup content was found to be higher t h a n normal. The lowering of the polymerization * Vysokomol. soyed. 8: No. 9, 1658-1659, 1966.
N . D . PRISHCHEPA et al.
1830
temperature had promoted an increase in CH2-group content. The variation was determined from the ratio of the optical densities of the methylene and phenyl group absorption bands. I n specimens produced at 0 ° in toluene, this ratio is 0"805, and at --78 ° D~86o/Dso2,: 1"935. For polymers prepared in ethylchloride at --50 and --130 °, D286o/Ds,~o is 0"935 and 3 respectively.
J t
f
f
8
8 /O-e
4
2
0
NMR spectra of specimens a a n d b. This increase in the methylene-group content of PMS was confirmed by NMR analysis. The Figure shows the NMR spectra of specimens a and b (D286o/Dso2o for specimen a was 0"805, and for specimen b, 1"5). The measurements were performed on an NMR spectrometer type 5535 working at a frequency of 40 Mc/s; the solvent was CCI~, the standard Si(CHs)4. I n the NMR spectrum ef specimen b the intensity of the peak with the chemical shift 1"2 v (CHI groups in the paraffin chain) had increased as compared with the corresponding peak in the spectrmn of specimen a. For the peak with the chemical shift 2"25 v (CHa groups combined in the benzene ring) the intensity had diminished. According to structural X-ray analysis PMS specimens containing the higher CH~ group content had a slightly crystalline structure. On the basis of the above data we suggest the following reaction for the formation of the polymer" ,~CH2--CH
~, -'-..,CH2--CH2
CH2
This can be regarded as a new example of polymerization with migration of the hydro. gen atom. Translated by V. ALFORD