Reactive Oligomers - American Chemical Society

17 Characterization of Hydroxyl-Terminated Liquid Polymers of Epichlorohydrin Downloaded by UNIV OF SOUTHERN CALIFORNIA on June 20, 2016 | http://pubs.acs.org Publication Date: July 9, 1985 | doi: 10.1021/bk-1985-0282.ch017

SIMON H . Y U Avon Lake Technical Center, The BFGoodrich Company, Avon Lake, O H 44012

Hydroxy1-terminated epichlorohydrin (HTE) liquid polymers are synthesized by a cationic ring-opening polymerization of epichlorohydrin in conjunction with a glycol or water as a modifier. Cyclic oligomers were removed by extraction. HTE liquid polymers free from cyclic oligomers are characterized by gel permeation chromatography, infrared, C and H NMR and field desorption mass spectrometry, and chemical titrations. The functionality and the spectroscopic data are consistent with the general structure I for the polymer made using ethylene glycol as a modifier. One unit of modifier is incorporated into the polymer chain and the functionality of the polymer is the same as that of the modifier. The terminal hydroxyl groups are predominately secondary; there are some head-to-head and tail-to-tail linkages. The results provide structural evidence that the polymerization proceeds via a polyaddition mechanism by propagating simultaneously from both ends of the difunctional modifier. 13

H-*-0CHCH - ^ n r - 0CH CH 0-- 1 2 0 0 ) , including commercial Hydrin 10 l i q u i d polymers, were removed by extraction. The functionality of the l i q u i d polymer was then determined, and structures are proposed as determined by i n f r a r e d , carbon-13 and proton NMR, and f i e l d desorpt i o n mass spectroscopic analyses. n

Experimental HTE l i q u i d polymers were synthesized by cationic ring-opening polymerization of epichlorohydrin (ECH) i n the presence of water or ethylene g l y c o l (EG) as a modifier ( 1 ) . C y c l i c oligomers were removed by extraction. After extraction, the l i q u i d polymers were e s s e n t i a l l y free from c y c l i c oligomers as determined by gel permeation chromatography (GPC) (Figure 1 ) . Hydroxyl numbers were determined by acetylation with an acetic anhydride-pyridine mixture. GPC analysis was c a r r i e d out at 40°C using a Waters GPC Model 200 instrument with columns packed with Styrogel [1Q A (4 f t ) , 10 A (2 f t ) , 10*A (2 f t ) , 1 0 * - 1 0 A (A f t ) , 10 A (4 f t ) , and 1 0 - 1 0 A (A f t ) ] . THF was used as a solvent. Molecular weights were c a l i b r a t e d with respect to polystyrene. Molecular weights of several l i q u i d polymers were also determined by vapor-pressure osmometry (VPO) using a Corona Wescan molecular weight apparatus. FT infrared spectra were recorded with a Nicolet 7199 spectrometer. Samples were prepared Q

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Harris and Spinelli; Reactive Oligomers ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

Downloaded by UNIV OF SOUTHERN CALIFORNIA on June 20, 2016 | http://pubs.acs.org Publication Date: July 9, 1985 | doi: 10.1021/bk-1985-0282.ch017

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Liquid Polymers of Epichlorohydrin

by applying a thin coat of l i q u i d polymers on a KBr c r y s t a l . Carbon-13 NMR spectra were acquired at 20.1 MHz using a Bruker WP-80 spectrometer. Liquid polymers were examined as a 20 wt. % solution in benzene-d$ or chloroform-d with internal tetramethylsilane reference at 3 0 ° C . Proton NMR spectra were acquired at 200.13 MHz using a Bruker WH-200 spectrometer, in chloroform-d at 3 0 ° C . Trichloroacetylisocyanate was used as a derivatizing agent (19). F i e l d desorption mass spectra were obtained with a Varian MAT 311A mass spectrometer in the f i e l d desorption mode. The samples were dissolved in either methanol or tetrahydrofuran. The solutions were then saturated with s o l i d lithium bromide so that the l i t h i a t e d molecular ions [MLi]+ were produced during analysis. Results and Discussion Functionality. For reactive l i q u i d polymers, the most important property i s the f u n c t i o n a l i t y . Functionality i s determined from number average molecular weight (M ) and hydroxyl number by the following equation: n

F

n = Hydroxyl Equivalent Weight - M x Hydroxyl Number 56,100 n

The hydroxyl number i s defined as the milligram equivalent of KOH per gram of the polymer, where a mole of KOH i s equivalent to one mole of hydroxyl group. According to GPC analysis, lower molecular weight HTE l i q u i d polymers (Mn1200) contain 10-20 wt. % of c y c l i c oligomers. Without the interference of c y c l i c oligomers, the determination of functionality of lower molecular weight HTE polymers i s straightforward. They are difunctional (Table I ) . In contrast, higher molecular weight HTE l i q u i d polymers containing c y c l i c oligomers show a bimodal molecular weight d i s t r i b u t i o n by GPC. The functionality calculated from the observed Mp varies from 0.5 to 1.5. After the c y c l i c o l i g o mers are removed by extaction, higher molecular weight l i q u i d polymers no longer exhibit bimodal d i s t r i b u t i o n and the Mp i s nearly twice that of the observed ffi p r i o r to the extraction; the functionality determined i s F = 2.0 (Table I ) . The M of several HTE polymers free from c y c l i c oligomers has also been determined by vapor pressure osmometry (VPO). For higher molecular weight HTE polymers, M ' s obtained from GPC are the same as those obtained from VPO. n

n

n

n

n

Infrared spectra. An FT infrared spectrum of HTE l i q u i d polymer (ff ~500) i s shown in Figure 2. A l l spectra of HTE polymers show c h a r a c t e r i s t i c absorptions: a broad band at 3530 cm"* for the hydroxyl stretching, three bands at 2958, 2913, and 2875 cm" assigned to the carbon-hydrogen stretching, an extremely strong n

1

1



202

REACTIVE OLIGOMERS

Figure 1.

GPC Curves of Hydrin 10 Liquid Polymers Before and A f t e r Extraction


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Table I .

203

Functionality of Hydroxy1-Terminated Epichlorohydrin Liquid Polymers( )


a

HTE 500 Lower molecular weight polymers containing no c y c l i c oligomers. Mn by GPC 623 OH Number 175 Functionality 1.9 Mn by VPO 527

HTE 1000

HTE lOOOAW

HTE 2000 A B Higher molecular weight polymers before extraction, flh by GPC 1,500 1,220 OH Number 56 57 Functionality 1.5 1.2

HTE 3000 A B

1,430 38 0.97

1,390 48 1. 2

1,530 34 0.93

Higher molecular weight polymers _ after extraction. Mn by GPC 2,320 1,920 OH Number 56 62 Functionality 2.3 2.1 Mn by VPO 2,300 —

3,070 37 2.0 2,960

2,750 45 2.2

3,610 27 1.8

1,030 118 2.2

1,130 114 2.3 874

C

Hvdrin 10X2 Hvdrin 10X1 Commercial polymers before extraction 1,570 Mn by GPC 1,700 OH Number 32 11 Functionality 0. 97 0.5 Commercial polymers after extraction Mn by GPC 4,080 11,800 OH Number 23 8.2 Functionality 2. 1.7 Synthesized l i q u i d polymers are designated as HTE followed by M . Hydrin 10 l i q u i d polymers are commercially available from BFG. b. HTE 1000A was synthesized using water as a modifier, other synthesized polymers using ethylene g l y c o l as a modifier. n

Table I I .

Ratios of Infrared Absorbances(a)

OH/CO CH/CO CC1/C0 HTE Liquid Polymer 0.0^0.7 0.38 0.37 PECH Elastomer 0.0 0.31 0.35 (Hvdrin 100) a. The absorbances of OH at 3530, CH at 2875, CO at 1125, and CC1 at 747 cm" . 1


REACTIVE OLIGOMERS

204

1

band at 1125 c n r assigned to the single bond carbon-oxygen stretching for ether linkages in the polymer chain and a doublet at 747 and 710 cm" attributed to the carbon-chlorine s t r e t c h ings for trans and gauche configuration, respectively. As the molecular weight of l i q u i d polymers increases, the hydroxyl absorpt i o n becomes weaker. For higher molecular weight Hydrin 10X2 ( ^ ^ 1 2 , 0 0 0 ) , the hydroxyl band nearly disappears. Table II summarized the r a t i o s of major absorbances of HTE l i q u i d polymers. Only the r a t i o of hydroxyl absorbance i s sensit i v e to the molecular weight, whereas the other two r a t i o s are independent of i t . For comparison, the r a t i o s of absorbances of high molecular weight elastomers (Hydrin 100) made by a coordination catalyst (R3AI/H2O) are also shown in Table I I . No hydroxyl absorbance i s detected. The two r a t i o s of CH/CO and CC1/C0 absorbances of HTE l i q u i d polymers match well with those of elastomers and are c h a r a c t e r i s t i c feature of polyepichlorohydrin.


1

Carbon-13 NMR spectra. A carbon-13 NMR spectrum of HTE polymer (MpSsTSOO) i s shown in Figure 3. The carbon-13 NMR spectra of HTE polymers show the carbon chemical s h i f t s at 79.3 and 72.7 ppm for the backbone and the terminal methine carbons respectively, at 43.9 and 46.2 ppm for the backbone and the terminal chloromethyl carbons, respectively, and in the range of 69.7-72.0 ppm as a multiplet for the methylene carbon. It i s a c h a r a c t e r i s t i c feature of hydroxyl-terminated polyethers that the terminal carbon exhibits a u p - f i e l d s h i f t due to the substituent effect of the hydroxyl group, whereas the |0 carbon(s) to the terminal hydroxyl group exhibits a down-field s h i f t (Table I I I ) . The terminal methine carbon also suggests that the hydroxyl groups are predominantly secondary.

Table I I I .

Hydroxylterminated Polyether Epichlorohydrin Ethylene Oxide Oxetane Tetrahydrofuran Propylene Oxide

Substituent Effect of Hydroxyl Groups on Carbon Chemical Shifts of Polyethers

-Carbon1. ppm Backbone Terminal 79.3 72.7 70.5 61.6 68.4 60.0 70.4 61.8 75.8 66.8 75.3 65.6

/3 -Carbon . ppm Backbone Terminal Reference This study 43.9 46.2 21 70.5 72.5 24 31.0 33.8 29.7 22 26.5 23 17.5 19.7

The complicated pattern for the methylene carbon of the polymers indicates the presence of an i r r e g u l a r structure of head to head and t a i l to t a i l linkages. On the other hand, the uniformly head to t a i l structure of polyepichlorohydrin elastomers made by the coordination catalyst shows a doublet for the methylene carbon at 70.2 and 70.0 ppm (21). No peak corresponding to the terminal methine or chloromethyl carbons i s detected in elastomers.


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Proton NMR spectra. Since a l l protons of HTE polymers show the resonance peaks at 3.4-4.1 ppm, no additional s t r u c t u r a l informat i o n can be derived from the proton NMR spectra. However, when HTE polymers are derivatized by trichloroacetylisocyanate, the resonance peaks of methylene and methine protons adjacent to the terminal hydroxyl groups s h i f t downfield to 4.4 and 5.1 ppm corresponding to the primary and secondary alcohols, respectively (Figure 4). The proton NMR spectra of the derivatized HTE polymers show that more than 90% of the terminal hydroxyl groups are secondary. FD Mass spectra. A FD mass spectrum of HTE polymers synthesized in conjunction with ethylene g l y c o l i s shown in Figure 5. The numbers shown indicate the units of ECH incorporated per polymer chain. The spectra are s l i g h t l y complicated by the * c i and C1 isotope patterns. A major series of species A with molecul a r weight of (62 + 92.5n) corresponding to [EG + n(ECH)] i s i d e n t i f i e d . A minor series of species B with molecular weight of (18 + 92.5n) corresponding to [H2O + n(ECH)] i s also detected as impurities due to the presence of trace amount of water during the polymerization. This series of impurities can be eliminated by careful precluding water i n the polymeriation system. Species B become the predominant series in HTE polymers synthesized i n conjunction with water (Figure 6). The FD mass spectra provide qualitative d i s t r i b u t i o n of v a r i ous species i n HTE polymers. Most importantly, the spectra also provide the s t r u c t u r a l information to prove the incorporation of one unit of modifier, ethylene g l y c o l or water, i n HTE polymers. This i s also the f i r s t analysis that distinguishes HTE polymers synthesized i n conjunction with ethylene g l y c o l and water. The incorporation of one unit of modifier into the polymer chain has been estimated semi-quantitatively with *H NMR method for the copolymerization of tetrahydrofuran and propylene oxide i n conjunction with 1,4-butanediol as a modifier (7). 5

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Proposed structures. The functionality and the spectroscopic data are consistent with the general structures as shown. Ethylene g l y c o l as a modifier:

H-£- 0CHCH --)nr0CH2CH2b-f-CH2CH0-4nH 2

CH C1

CH C1

2

2

Water as a modifier: H-f-0CHCH -)nr0 — f - C ^ C H O - ^ H CH C1 CH C1 2

2

2

The proposed structures are consistent with the polyaddition mechanism of cationic ring-opening polymerization of ECH i n conjunction with a modifier (18). The polymer chain propagates simultaneously at both ends of the difunctional modifier through polyaddition of monomers. Consequently, one unit of modifier i s incorporated into the polymer chain and the functionality of the


206

REACTIVE OLIGOMERS

M *500 n

c d c e 4CH CH0-^ CH CH0H 2

2

CH CI o

CH CI


2

Figure 3.

2

b

Carbon-13 NMR Spectrum (20.1 MHz) of HTE Liquid Polymer

M c500 200.13 Mi in CDCIj n

-CH CH02

CH CI 2

5.1 ppm 2 OH #

TMS

4

Figure 4.

"T-

3

Proton NMR Spectrum of Derivatized HTE


1

O ppm

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1000

:

A:EG4(ECH)„

6

B.MjO^IECM),,

* 1

341. \—r-S—i—i—r1—i—i—i—i

1000 Downloaded by UNIV OF SOUTHERN CALIFORNIA on June 20, 2016 | http://pubs.acs.org Publication Date: July 9, 1985 | doi: 10.1021/bk-1985-0282.ch017

r

400

^500l

625

M

500

®

lOOOn

?500^

650

®

IJ * .i

i — r — | — 1 — r — 1 — i — r — i — r

700

750

800

®

654 871 i—i—r*^r"

i 904 r i i—i i i i i—i—i—i—i—i—i—i i— i — r -

650 Figure 5.

550

717

1 — i — I — i — r * i — i — i — r - n669 r — i — i — i

600

1 1 1 .

900

1000

950

1050

FD Mass Spectrum of HTE Liquid Polymer (EG as a modifier)

671

KXXOi B HgO + (ECH)n

579 577

>> 500

453 469 ^ 4 9 9

369

> 1

-I—I—i—|*

450.

400

KX)0

*1?557

1 — I — i — I — f t

500

*i—r

550

600 619 -f-r-V

639

1

650

600

763

I

5 0 0

1

.

^

.4

T . |

• 693 TIT 731 700 Figure 6 .

853Bl 750

800

850

@ 90Z 9 » 900

*>' 950

FD Mass Spectrum of HTE Liquid Polymer (Water as modifier)


REACTIVE OLIGOMERS

208

polymer i s the same as that of the modifier. The proposed structures against the monocation mechanism which suggests only one end of the difunctional modifier participates and a modifier unit i s incorporated at the head of the polymer chain (5.6). Acknowledgments The author g r a t e f u l l y acknowledges the support of t h i s work by BFGoodrich Staff Technical Services: J . L . Dorsch for C NMR, J . P . Shockcor for H NMR, 3.W. Ryan for FT-IR, 3.B. Haehn for GPC, D . J . Harmon for VPO, R.P. Lattimer for FD-MS, and M. Chesler for chemical a n a l y s i s . Also the laboratory support of D.A. Versace and encouragement of D . E . Mackey and valuable discussions with M.P. Drefuss and Y. Okamoto. 1 3


l

Literature Cited

1. Dreyfuss, M.P. U.S. Patent 3 850 856, 1974. 2. Young, C.I.; Barber L.L. U.K. Patent Application 2 021 606, 1979. 3. Aelony, D. U.S. Patent 4 284 826, 1981. 4. Bruson, H.A.; Rose, J.S. U.S. Patent 3 269 961, 1966. 5. Manser, G.E.; Rose, D.L. "Synthesis of Energetic Polymers", SRI Project PYU 8627, 1981. 6. Manser, G.E. U.K. Patent Application 2 101 619 A, 1983. 7. Hammond, J.M.; Hooper, J.F.; Robertson, W.G.D. J. Polym. Sci. Part A-l 1971, 9, 265. 8. Alvarez, E.J.; Hornof, V.; Blanchard, L.P. J. Polym. Sci. Part A-l 1972, 10, 1895 and 2237. 9. Baijal, M.D.; Blanchard, L.P. J. Polym. Sci. Part C 1968, 157. 10. Blanchard, L.P.; Baijal, M.D. J. Polym. Sci. Part A-l 1967, 5, 2045. 11. Blanchard, L.P.; Singh, J.; Baijal, M.D. Can. J. Chem. 1966, 44, 2679. 12. Taganov, N.G.; Korovina, G.V.; Entelis, S.G. Polym. Sci. USSR 1980, 22, 1717. 13. Entelis, S.G.; Korovina, G.V. Makromol. Chem. 1974, 175, 1253. 14. Dickinson, L.A. J. Polym. Sci. 1962, 58, 857. 15. Murbach, W.J.; Adicoff, A. Ind. Eng. Chem. 1960, 52, 772. 16. Goethals, E.J. Adv. Polym. Sci. 1977, 23, 104. 17. Yamashita, Y.; Kawakami, Y. Yuki Gosei Kagake Kyokaishi 1978, 36, 183; Chem. Abstr. 1978, 89, 248431. 18. Okamoto, Y. Polym Reprints 1984, 2, No. 1, 264. 19. Groom, T.; Babiee, J.S. Jr.; Van Leuwen, G.B. J. Cellular Plastics 1974, Jan/Feb, 43. 20. Steller, K.E. in "Polyethers"; Vandenberg, E.J., Ed.: ACS SYMPOSIUM SERIES No. 6, American Chemical Society: Washington, D.C. 1975; p. 136. 21. Bayer, E.; Zheng, H.; Albert, K.; Geckeler, K. Polym. Bull. 1983, 10, 231. 22. Pruckmayr, G.; Wu, T.K. Macromolecules 1978, 11,265. 23. Mochel, V. D.; Bethea, T. W.; Futamura, S. Polymer 1979, 20,65. 24. Yu, S. H. unpublished data. RECEIVED

March 5, 1985


Reactive Oligomers - American Chemical Society

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