Control synthesis of isocyanate and alkoxy-silane terminated macromers

Control Synthesis of Isocyanate and Alkoxy-Silane Terminated Macromers

FRANCOISE SURIVET,' THANH M Y LAM," and JEAN-PIERRE PASCAULT'

'Centre de Recherches Corning EUROPE, 7 bis avenue de Valvins, 77 21 1 Avon Cedex, France, 'Laboratoire des Matbriaux Macromolbculaires-URA CNRS 507, lnstitut National des Sciences Appliqu6es de Lyon, 20, avenue Albert Einstein, 69 621 Villeurbanne Cedex, France

SYNOPSIS

The kinetics of the reactions in bulk of 4,4'-dicyclohexyl methane diisocyanate ( H12 MDI) and 5-isocyanato-1,3,3-trimethylcyclohexylmethyl isocyanate or isophorone diisocyanate (IPDI) with benzylic alcohol (BZA) and a-hydroxy-o-methyl ether-terminated polyethylene oxide PEO (au = 350) were studied by size exclusion chromatography (SEC) and 13C nuclear magnetic resonance ( 13C-NMR). The substitution effect is exhibited in the case of H12 MDI reactivity. The kinetic constants were calculated by a numerical method. The second-order kinetic mechanism was shown to be valid. In the IPDI case, the cycloaliphatic isocyanate group is shown to be more reactive than the aliphatic group in our conditions, without catalysis, in agreement with previous results from the literature, obtained by 'H- and 13C-NMR without any catalyst. The reactivity ratio is found to be on the order of 3. This difference in reactivity of the two isocyanate groups is used for the control synthesis of isocyanate and alkoxy-silane-terminated macromers. Keywords: reactivity of isocyanate group IPDI H12 MDI urethane alkoxy-silane

INTRODUCTION

The hydrolysis and condensation reactions of alkoxy-silanes lead to the formation of an oxide net- work, suggesting a possible way to form glass, ceramic, and hybrid organic-inorganic materials. In- vestigations of the sol-gel process were focused on the use of silicon alkoxides and on the use of silane- terminated macromers. These macromers can be prepared by reacting two types of components: the organic one can be a macrodiol or a polyurethane and the inorganic one may be an organosilane with two classes of functionalities. The general formula of an organosilane is Rn-Si-X(4-n). X is a hydro- lyzable group involved in inorganic reactions and R a nonhydrolyzable organic radical that possesses a functionality which enables the coupling agent to bond with the macrodiol or the polyurethane. The products that we are going to synthesize will be used

* To whom all correspondence should be addressed. Journal of Polymer Science: Part A Polymer Chemistry, Vol. 29, 1977-1986 (1991) 0 1991 John Wiley & Sons, Inc. CCC 0%37-624X/91/131977-10$04.00

as model compounds in order to investigate hydrolysis and condensation reactions of alkoxysilanes. They were produced through the reaction of y-amino propyl triethoxysilane with polyurethane prepoly- mers with free isocyanate group. Model isocyanate- functionalized polyurethanes were prepared from mono-alcohols and diisocyanate using the stoichi- ometry ratio calculated to give a level of excess isocyanate functionality such that a molecule would have an average of one free isocyanate group. Di- isocyanate functionalized polyurethanes could be also prepared from a, w-diols and excess of diisocyanate.

Polyurethanes based on aromatic hard segments exhibit UV radiation induced discoloration which has been related to the structure of the aromatic diisocyanates used in the polymer. However, re- placing the aromatic diisocyanate with cycloaliphatic diisocyanates such as 4,4'-dicyclohexyl methane diisocyanate ( H12 MDI) or such as 5-isocyanato-1,3,3-trimethylcyclohexylmethyl isocyanate or isophorone diisocyanate ( IPDI ) improves light stability.'

1977

1978 SURIVET, LAM, AND PASCAULT

H12 MDI is an apparent symmetrical cycloali- a) H12MDIcme phatic diisocyanate. In the literature, substitution effects have been found for some symmetrical diiso-

phenylene; 2.9 for 44 ' diphenylmethane; 2 for 1-6 hexamethylene.2 ( k l / k 2 is the ratio of the first re-

cyanates with following values of k l / k 2 : 9.2 for p - I1 ti M U k'i D U

+ - + )--I D--(7

action rate constant of an isocyanate group to the X Y second reaction rate constant with n-butanol in toluene at 40°C with a triethylamine catalyst.) The situation is more complicated for H12 MDI because the commercial product is a mixture of three isomers as shown in Figure 1: cis-trans (65% ) , trans-trans (30% ) , and cis-cis (5% ) .3 No study about the relative reactivities of NCO groups in H12 MDI was found.

IPDI is an asymmetric cycloaliphatic diisocyanate. It has been shown by NMR spectroscopy and gas chromatography4 that the molecule consists of a mixture of two isomers, cis and trans, according to whether the NCO and CH2NC0 are cis or trans

b) IPDIcase

IA-Ic /

2

k'c \ ' D U

cis-cis

YA

Figure 2. Kinetic schemes for reaction of monoalco- hol with (a ) 4,4'-dicyclohexyl methane diisocyanate (HI, MDI) and (b) 5-isocyanato-1,3,3-trimethylcyclohexylmethyl isocyanate.

to each other on the cyclohexane ring (see Fig. 1). Estimates of the isomer ratio from 'H- and I3C-NMR and gas chromatography indicate similar values of about 72% of the cis isomer and 28% of the trans isomer.

In the literature, the existing results concerning C H 3 CH2-N=C=0 C NCOA > the relative reactivities of isocyanate groups of IPDI

are quite different. For the supplier, the aliphatic isocyanate group is about 10 times as reactive as the cycloaliphatic Cunliffe et al.4 have estimated the ratio kA/kc equal to 2.5 for the IPDI-n-butanol system at 60°C. ( k A / k c is the ratio of the reaction rate constant of the aliphatic isocyanate group to the reaction rate constant of the cycloaliphatic isocyanate group for IPDI as defined in Figure 2.) It has been found that the ratio decreases from 4 to 1 with an increase in the temperature from 40 to

N=C=O < NCOC )

&: C"3 CH3

CH3 <H2NC0

H

c i s t T a n s

~i~~~ 1. Configurational isomers of (a ) 4,4'-dicyclohexyl methane diisocyanate (HI* MDI) and (b) 5-isocyanato-1,3,3-trimethylcyclohexylmethyl isocyanate. 110°c.6

ALKOXY-SILANE TERMINATED MACROMERS 1979

These differences provide that experimental conditions, analytical methods, and kinetic mechanisms used for calculation are not identical. In fact, the nature of the most reactive group is to be discussed. It has been shown that the identity of the more reactive NCO group is catalyst dependent, being the secondary cycloaliphatic group in the absence of added catalyst or when the catalyst is dibutyl tin dilaurate, and the primary aliphatic group with 1,4- diazabicyclo ( 2,2,2) octane (DABCO) or triethyl amine.6-10 In their kinetic study of reaction between IPDI and amino diols in toluene at 50°C, Gerard et al." have identified the primary aliphatic NCO group as the more reactive group, with a I z A / l z c ratio equal to 2.5, but it is possible, in this case, that an amino- diol has the same behavior as the tertiary amine catalysts.

The mechanism and kinetics of the alcohol-isocyanate reaction have been analyzed and reviewed by several investigator^.'^-'^ Although the reaction is approximately of second order, it has been dem- onstrated that more complex equations are neces- sary and a variety of formulas have been used in- volving autocatalysis by alcohol and urethane as well as tertiary amines or external catalysts.16 In our case, the presence of a catalyst would lead to a reaction between the isocyanate and the amine (7-APS) too fast and too exothermic. So the reaction for pre- paring silane-terminated macromers would be too

Table I. Characteristics of the Different Monomers Used

difficult to control. Therefore, no catalyst was used in our study.

Because the reactivity ratio of the two isocyanate groups of diisocyanate is important for the synthesis of these macromers, we have first studied the reactivity ratio with a mono-alcohol. Size exclusion chromatography (SEC) and 13C nuclear magnetic resonance (NMR) are used as analytical techniques. The advancement of the reaction was determined by SEC analysis by measuring the monomer peaks (see the next section). The SEC technique was not yet mentioned in the literature for kinetic studies of isocyanate-alcohol reactions. We have used benzylic alcohol because it gives a good signal in SEC analyses. SEC is a crude technique for this type of measurement but it will be also very useful when determining the evolution of the molar mass of the prepared polyurethanes when a,o-diols will be used instead of mono alcohol. The relative reactivities of isocyanate groups are calculated from experimental data via a mechanism of second-order kinetics. The calculations were performed using a microcomputer with the Runge-Kutta numerical method.

EXPERIMENTAL

Starting Reagents Isophorone diisocyanate (IPDI) from Aldrich and 4,4'-dicyclohexyl methane diisocyanate ( Hlz MDI )

Monomers

Molecular Melting Glass Transition Weight Temperature Temperature Purity

Formulas (g mol-') ('C) ("C) (%) Supplier

Benzylic Q C H , O H 108.1 -15 - 99 Aldrich

a-Alcohol-o-methyl CH3-fOCHz- CH,-),-OH 350 -8 -95 99 Aldrich

alcohol (BZA)

ether terminated polyethylene oxide (PEO)

diisocyanate (IPDI)

Isophorone 222 - -99 99 Aldrich

H:%Nco H3C CHJ'JCO

4,4'-Dicyclohexyl O C N O C H , e N C O 262 - -75 99 Bayer methane diisocy anate (HI2 MDI)

y-Amino propyl NI-&-fCHz)a- Si(OCH,H,), 22 1 - -130 98 Aldrich triethoxy silane (Y-APS)


from Bayer were used without further purification. Benzylic alcohol (BZA) and a-hydroxy-w-methyl ether terminated polyethylene oxide (PEO) from Aldrich were dried under vacuum for 48 h at 60°C before use. The formulas, molecular weight, and melting and transition temperatures are listed in Table I.

Characterization

The analyses of the soluble products were made on a Waters chromatograph equipped with a 6000A pump, U6K injector, and a double detector (UV at X = 254 nm and differential refractometer R401) . The eluant used was tetrahydrofuran (THF) and the separation was carried out in four p styragel col- umns ( lo3 A + 500 A + 100 A + 100 A) with an elution rate of 1.5 ml/min. The approximate average molecular weight ( I@n, I@,) was calculated using a polystyrene calibration. Calibration of diisocyanates and alcohols is also made and show that SEC peak heights are proportional to concentration.

13C-NMR spectra were taken with a Bruker AC 200 spectrometer at 50 MHz in deuterochloroform as the solvent and with tetramethyl silane (TMS) as the internal reference.

n u U

I

15

8h

2h

I

20

I 30

t, ( m i n )

Figure 3. SEC chromatograms at different reaction times for the Hlz MDI-BZA system in stoichiometric NCO/OH = 2 at T = 80°C.

100 1

0 2 4 6 8 10

time (h)

Figure 4. Monomer disappearance versus reaction time at T = 80°C for the BZA-HIz MDI reaction: (0) X = (II),/ (1110; ( 0 ) A = ( A ) t / ( A ) o .

Reactions

The following different reactions are involved in this paper:

diisocyanate and mono-alcohol reactions for kinetic study of reactivities of isocyanate groups. diisocyanate and mono-alcohol reactions for synthesis of isocyanate terminated macromers.

0 synthesis of silane terminated macromers.

The last type of reaction will be treated later and presented with results concerning difunctionalized &isocyanate terminated macromers. In the first type of reaction, IPDI or H12 MDI reacted with mono- alcohol with a stoichiometric ratio NCO/OH = 2 at 80°C in bulk without catalyst. The mixture was stirred under vacuum, then heated for 24 h. At this time, a size exclusion chromatography (SEC) of the materials showed a complete disappearance of the mono-alcohol molecules and no more evolution of the diisocyanate peak: so, hydroxyl groups have en- tirely reacted. For the kinetic study, the results are presented and discussed now.

RESULTS AND DISCUSSION

Kinetic Study of HI? MDI-BZA Reaction in Bulk

Examples of the chromatograms obtained for the H12 MDI-BZA system at 80°C at different reaction times are shown in Figure 3. At t = 0, two peaks are observed ( i ) a peak at t, = 20.28 min attributed to


H12 MDI and (i i) a peak at t, = 21.53 min attributed to BZA. As the reaction time increased, two new peaks appeared the first one attributed to the reaction product HI2 MDI-BZA (t , = 19.10 min) and a second one to the dimer BZA-H12 MDI-BZA (t , = 18.23 min).

The disappearance of the two monomers can be expressed by X = (II),/(II), and A = ( A ) , / ( A ) , , where (11) and ( A ) are respectively diisocyanate and mono-alcohol concentrations, proportional to the heights of the peak h (b is the initial height of the peak ) .

X and A as functions of time are shown in Figure 4. We observed that the mono-alcohol molecules disappeared more rapidly than the diisocyanate molecules and after 24 h, no more residual mono- alcohol molecule is observed. Since SEC allows the separation of molecules, this representation does not exhibit the disappearance of the isocyanate groups.

The disappearance of the hydroxyl groups is equal to that of the monomer since we have used a mono alcohol for our kinetic studies. So we can write:

The situation is more complex for the diisocyanate monomer. If there is equireactivity of all NCO groups and no substitution effect, the probability of finding a diisocyanate molecule is equal to the probability of having two unreacted isocyanate groups on the same molecule.

0 2 4 6 8 10

time (h)

Figure 5. Comparison between the (0) experimental values of A = At/Ao (0) and the ( 0 ) calculated values of A [ eq. (9 ) ] : A = 2 fi - 1 for the BZA-HI2 MDI system.

There is a relation between (NCO), and ( A ) ,

In our case, we want to prepare isocyanate-terminated macromers, so the initial conditions are defined as

From eqs. ( 4 ) and ( 5 ) , we obtained

or

(NCO),= ( A ) , [ 1 +- I:;:] ( 7 )

and from eqs. (5) and ( 7 ) we have:

If there is no substitution effect, we must have from eqs. (2) and (8) the following expression:

2 f i - l = A (9)

In Figure 5, we give the variations in the A experimental values compared to the calculated ones from eq. (9) in the case of the H12 MDI-BZA reaction. The two curves are quite different; the experimental points are higher than the calculated values. This means that the hydroxyl groups did not disappear as fast as expected from the assumption of equireactivity of the two isocyanate groups. From this result, we can conclude that after the reaction of the first NCO group, the reactivity of the second NCO is lower.

For calculating the ratio of reactivity, we have tried different kinetic schemes. Using different values for the initial reactivities of the NCO groups according as they are in cis or trans positions and taking into account the percentage of the three isomers, and a mechanism with or without the catalytic effect of the hydroxyl and urethane groups, we were not able to obtain an agreement between experimental and calculated values of the different species formed during the reaction. The best fit is given by a simple model, based on a second-order kinetic law,


with identical initial reactivity of the two NCO groups and a substitution effect once the mono-urethane is formed. So, on the basis of the scheme in Figure 2, we can write the the following equations:

11 + OH % MU

MU + OH 2 DU

with

X and A as previously defined

- 2KiXA dX dt

dA - 2KlXA + NK,YA dt

-= dY 2 K J A - N K I Y A dt

dZ - - - K;YA dt

We have the following relations between X , Y , 2, and A :

So, we can calculate values for Y and 2

Z = X - A (16)

Y = 1 - X - 2 o r Y = l - A - 2 2 ( 1 7 )

The constants are obtained by numerical calculations using the Runge-Kutta method. The results of the calculations are given in Figure 6. The best N value was found to be equal to 0.5. The kl value (2.17 X mol-' kg s-l) is on the same order as the kinetic constants obtained in solution by Cun- liffe et al.4 ( k1 = 2.21 X mol-' L s-l at 6OoC in heptane ) for IPDI-propanol reactions.

Kinetic Studies of IPDI-BZA Reaction in Bulk

In this case, we know that IPDI is a nonsymmetrical diisocyanate. The experimental values of X and A obtained from SEC experiments are given in Figure 7 . A simple scheme based on a second-order law is used as in the preceding case. As the two isomers are not isolated, we suppose that the rate constants are the same for them. Moreover, Gerard et al." have observed that the isocyanate groups IA and Ic in the mono-urethanes YA and YC (see Fig. 2 ) reacted with hydroxyl groups with the same rate. So we shall use only one value for the rate constant for the reactions of mono-urethane (MU) to obtain di- urethane (DU) , kh = k b = k3.

I A - IC + OH .% MU1

IA - Ic + OH !% MU2

MU + OH 2 DU

100

n w

N

U

; X

50

0

1 0 0

n w

4

U

50

0

0 2 4 6 8

t i m e ( h 1

Figure 6. Comparison between the experimental values (broken curves) and the calculated values (full curves) of ( 0 ) X, (0 ) Y , ( A ) 2, and (0 ) A for the BZA-HI2 MDI system.


with

N = - k A

kc

Ki = kc ( OH 10 K3 = k 3 ( 0 H ) o

X , Y and A as previously defined

2 = Z A + Zc (as defined in Figure 2 )

we can write

dX dt

= KiXA(1 + N ) --

dA - K I X A ( l + N ) + K3YA ( 1 9 ) dt

- _ dY - K , X A ( ~ + N ) - K ~ Y A ( 2 0 ) dt

- = dz K3YA dt

The kinetic constants were calculated by numerical method (Runge-Kutta) and the results of the calculation are given in Figure 8. We find that k, (2.7 X l op5 mol-' kg spl) is a little superior to the value obtained for H12 MDI (2.2 X lop5 mol-' kg s-'). The k3 value (1.8 mol-' kg s-l) is rela- tively large; this is due probably to the catalytic effect of the urethane group. This effect is not taken into account in the kinetic scheme. The N value is about 0.35, so we can say that the reactivity ratio is about

0 2 4 6 8 10

time (h)

Figure 7. Monomer disappearance versus reaction time at T = 8OoC for the BZA-IPDI reaction: (0 ) X = ( I I ) t / (II)o, ( 0 ) A = (A)t/(A)o.

1 0 0

n M

N

ji

W

i

5 0

1 0 0

r\

M

4 "

5 0

0

0 2 4 6 8

t i m e ( h 1

Figure 8. Comparison between the experimental values (broken curves) and the calculated values (full curves) of ( O ) X , ( O ) Y,(A)Z,and(O)AfortheIPDI-BZAsystem.

three in favor of the cycloaliphatic group. This ratio is on the order to these found in the literature for the temperature studied. In any case, the N value depends on the kinetic scheme used. Some authors evaluate the reactivity ratio by the ratio of Y A / Yc , this value is a function of time and generally is different from N .

Control Synthesis of Isocyanate Terminated Macromers IPDI was reacted with mono-hydroxy terminated polyethylene oxyde, PEO (Sn = 350 g/mol), with a stoichiometric ratio NCO/OH = 2 at a temperature of 8OoC for 24 h in bulk without catalyst.

Figure 9 shows the chromatogram of the final product. From this, and using an internal reference to determine the molar fraction of nonreacted diisocyanate, we find X = 0.17. Applying equations (14)-( 17) with A = 0 (corresponding to the total disappearance of hydroxyl groups, as shown in Fig.


PEO-IPDI - t = l h

PEO-IPDl t = 24h

PEO-IPDI t = O

YAPS

I I I

20 25 30

te ( m i n )

SEC chromatograms at different reaction Figure 9. times for the PEO-IPDI-yAPS system.

91, we have the molar fractions of mono-urethane Y = 0.66 and di-urethane Z = 0.17.

Figure 10 shows the I3C-NMR peaks of ioscyanate and urethane groups. Table I1 gives the indexations, based on references 6, 9, and 11 and the relative intensities.

This table shows that at the end of the reaction, the percentage conversion of cycloaliphatic group is 6596, while the value for aliphatic group is about 40%. The reactivity ratio is superior to 1.6 in favor of cycloaliphatic group. These results clearly confirm those of Ono et a1.8 obtained with 'H-NMR and those of Bialas et al.' obtained with 13C-NMR and confirm our choice of the kinetic model in the preceding section.

From Table 11, we have some relations between the &isocyanate X , the mono-urethane ( Y = YA) + Yc) and the di-urethane ( 2 ) at the end of the reaction.

X + Yc = 0.175 X 2

X + YA = 0.301 X 2

2 + YA = 0.32 X 2

2 + Yc = 0.204 X 2

These four equations do not give a unique set of solutions. Taking the value given by the SEC chromatogram, X = 0.17, we can estimate YA = 0.44, Yc

= 0.20 ( Y = 0.64) and 2 = 0.19. These values of Y and Z agree with those obtained above. In our experiments, the ratio Y A / Y c is equal to 2.2 at the end of the reaction.

This relative intensity depends on experimental conditions, in particular on the nature of the catalyst used. Our experiments were performed without catalysis. At the end of the reaction, the conversion of cycloaliphatic isocyanate group is 6596, while the value of aliphatic group is 40%. In the study by Bia- las et al., the catalyst used was dibutyl tin dilaurate and in this case, the conversion of the cycloaliphatic isocyanate group (with respect to the aliphatic group) was higher than in our case. Hatada et a1.6 have shown that when a dibutyl tin dilaurate catalyst was used, the reactivity of cycloaliphatic group be- came about 12 times higher than that of the aliphatic isocyanate group. The catalyst has not only an in- fluence on the reaction path, but also on the final products. If we had to give a value of reactivity ratio, N , of the two isocyanate groups, we would meet a confusion. As we have mentioned earlier, some authors take N as the ratio of degrees of conversion

e = equatorial

a = axial

CDCl3

kl r

1 0 0

b l

I I 1 I 1 4 0 1 3 0 1 2 0 150

6 ppm

Figure 10. 13C-NMR spectra of (a ) IPDI, (b) PEO- IPDI system after 24 h at 80°C, in deutochloroform as the solvent.


Table 11. System Determined by I3C-NMR

Relative Intensities of Isocyanate and Urethane Groups for the PEO-IPDI

Cycloaliphatic Aliphatic Cycloaliphatic Aliphatic c11 Cl, c11. ClT

6 ( P P d 122.92 122.06 154.14 155.42

Final percentage 17.5 30.1 32 20.4 Initial percentage 50 50 0 0

of the two isocyanate groups or the ratio of the two mono-urethanes Yc/ YA , whereas rigorously, N must be a ratio of two rate constants. This value is generally not given in the literature.

Use of Isocyanate Terminated Macromers to Prepare Silane Terminated Macromers

The product described above was dissolved in tetrahydrofuran ( mol for 100 mL) and immedi- ately combined with y-amino propyl triethoxysilane with a stoichiometric ratio NCO/NH2 = 1. The mixture was stirred at room temperature for 1 hr. The solvent was removed under a rotating evapo- rator at 40°C for 15 h. An IR spectrum of the products showed no unreacted isocyanate and a complete reaction.

The chromatogram of this silane terminated mac- romer is represented in Figure 9. Using the SEC previous results, we have the following weight dis- tribution:

PEO-IPDI-PEO: 0.17 mol with a functionality

PEO-IPDI-y-APS: 0.66 mol with a functionality

y-APS-IPDI- y-APS: 0.17 mol with a function-

equal to 0

of ethoxy silane groups equal to 3

ality of ethoxy silane groups equal to 6

corresponding to a product with well-defined characteristics: Mn = 1309, M, = 1494 expressed in PS standards molecular weight,

This product will be used in order to study the hydrolysis and condensation reactions of alkoxysilanes. This will be done in a later publication. The ideal product for this study will have the greatest percentage of PEO-IPDI- y-APS and the lowest amount of PEO-IPDI-PEO and y-APS-IPD1-y- APS corresponding to the lowest percentage of residual diisocyanate. This quantity depends on the relative reactivity of cycloaliphatic and aliphatic isocyanate groups, as we have shown earlier.

= 3.6 and fw = 4.0.

CONCLUSIONS

If we had used a tin catalyst in our synthesis of isocyanate terminated macromers, the percentage of residual diisocyanate would have been lower and these conditions would be better for obtaining a model to study silane reactions. However, the presence of this catalyst would lead to an uncontrolled reaction between the isocyanate and the amine (y- APS ) , so in order to prevent this possibility, we did not use a catalyst in the first step of the synthesis. In some experiments (which will be described in a later publication ) , macrodiols instead of monoal- cohols are used in order to form ceramic networks. In this case, we have a chain extension with a dis- tribution of molecular weights. Chain extension is controled by the relative reactivity of the isocyanate groups, but this time the chains are terminated ex- clusively by ethoxy-silane groups, with an unique functionality equal to 6. Work is in progress in our laboratory concerning the use of this alkoxy-silane terminated macromers to prepare ceramers networks.

This work was sponsored by the Corning Europe Com- pany. The financial support of this institution is gratefully acknowledged. We wish to thank Q. T. Pham, H. Watton, and R. Petiaud from CNRS (Solaize) for performing and discussing NMR experiments.

REFERENCES AND NOTES

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S. L. J. Cooper, Macromol. Sci. Phys., B17,621-629 (1980).

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VEBA CHIMIE, Brevet R. F. A. 22-MD-1176-6 (1976). 0. Lorenz, H. Decker, and G. Rose, Angew Makromol. Chem., 122 ,83 (1984). K. Hatada, K. Ute, K. I. Oka, and P. Pappas, J. Polym. Sci. Part A: Polym. Chem., 2 8 , 3019-3027 ( 1990). H. K. Ono, F. N. Jones, and S. P. Pappas, J. Polym. Sci. Polym. Lett. Ed., 23, 509-515 (1985). K. Hatada, K. Ute, and P. Pappas, J. Polym. Sci. Po- lym. Lett. Ed., 25,477-480 (1987). N. Bialas and H. Hocker, Makromol. Chem., 191 ,

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Received November 15, 1990 Accepted April 12, 1991

Documents

Control synthesis of isocyanate and alkoxy-silane terminated macromers