Chapter 1 Introduction
1.3 Polymer miscibility and interactions
Polymer blend phase behavior can be predicted or analyzed by inserting the
binary interaction model into the thermodynamic framework of either the Flory-Huggins theory or an appropriate equation-of-state theory. It is useful for evaluation of isothermal phase boundaries, miscibility maps, or phase separation by using the simplicity of the Flory-Huggins theory and equation-of-state. Recently, several polymer theoretical equations of state are available [24], and some have been applied to polymer solutions and blends [25]. However, the role of polymer interaction in determining the phase behavior of polymer blends is fascinating from a number of concerns. Polymer interactions are usually meaning “strong” specific, and orientation dependent. In polymer blends, most of it have been widely concerned with the following intermolecular or inter-segment forces:
(a) Strong dipoles (b) Hydrogen bonds
(c) Charge transfer complexes (d) Ionic interactions in ionomers
Polymer miscibility is based on the assertion that the free energy of mixing can be written in the following form:
(1-1)
The segmental interaction parameter χ is the “physical” interaction parameter and subscripts 1 and 2 refer to the blend components, while the ΔGH term reflects
free energy changes corresponding to specific interactions, most commonly, but not necessarily, hydrogen bonds. Nevertheless, hydrogen bonds are not easily characterized. There are two common experimental ways being able to characterized hydrogen bonds within polymers:
(a) Thermodynamic: Measurements depend upon thermodynamic changes in a system as a whole and can be related to molecular properties through the analyses of statistical mechanics, and these results are often model dependent and sensitive to various assumptions that have to made.
(b) Spectroscopic: Spectroscopy techniques can aid in the evolution of miscibility, specifically when the interactions induce a change in the material physical properties (e.g. glass transition temperature); such as a change can be measured by radiate energy, including spectroscopy of solid-state or liquid nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), Raman, XPS and others.
References
[1] Lichtenhan JD, Feher FJ, Gilman JW. Macromolecules 1993;26:2141-2 [2] Lichtenhan JD, Otonari Y, Carr MJ. Macromolecules 1995;28:8435-7 [3] Laine RM, Sellinger A. Macromolecules 1996;29:2327-30
[4] Mather PT, Haddad TS, Oviatt HW, Schwab JJ, Chaffee KP, Lichtenhan JD.
Polym Prepr 1998;39:611-2
[5] R. H. Baney, M. Itoh, A. Sakakibara, and T. Suzuki, Chem. Rev. 95, 1409 (1995) [6] X. Zhang and L. Shi, Chin. J. Polym. Sci. 5, 197 (1987)
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[9] G. E. Maciel, M. J. Sullivan, and D. W. Sindorf, Macromolecules 14, 1607 (1981) [10] G. Engelhavdt, H. Jancke, E. Lippmaa, and A. Samoson, J. Organomet. Chem.
210, 295 (1981)
[11] C. L. Frye and W. T. Collins, J. Am. Chem.Soc. 92, 5586 (1970)
[12] V. Belot, R. Corriu, D. Leclerq, P. H. Mutin, and A. Vioux, Chem. Mater. 3,127 [13] H. Adachi, O. Hayashi, and K. Okahashi, Japanese Patent Kokoku-H-2-15863 [14] H. Adachi, O. Hayashi, and K. Okahashi, Japanese Patent Kokai-S-60-108841 [15] E. Adachi, Y. Aiba, and H. Adachi, Japanese Patent Kokai-H-2-277255
[16] Y. Aiba, E. Adachi, and H. Adachi, Japanese Patent Kokai-H-3-6845
[17] F. Shoji, R. Sudo, and T. Watanabe, Japanese Patent Kokai-S-56-146120 [18] E. Imai, H. Takeno, Japanese Patent Kokai-S-59-129939
[19] T. Mishima, and H. Nishimoto, Japanese Patent Kokai-H-4-247406 [20] Y. Saito, M. Tsuchiya, and Y. Itoh, Japanese Patent Kokai-S-58-14928 [21] T. Mine and S. Komasaki, Japanese Patent Kokai-S-60-210570
[22] Lichtenhan JD, J. J. Schwab, and W. A. Reinerth, Sr., Chem. Innovat. 1, 3 [23] M. W. Ellsworth and D. L. Gin, Polym. News 24,331
[24] Dee, G. T. and Walsh, D. J. Macromolecules 1988,21, 811 [25] Flory, P. J. J. Am. Chem. Soc. 196, 87, 1833
Chapter 2 The syntheses of octaphenol-POSS
Scheme 2-1. The syntheses of octaphenol-POSS
2.1 Experimental section
Materials
Q8M8H was purchased from Hybrid Plastics Co. Platinum divinyltetramethyldisiloxane complex, Pt(dvs) and acetoxystyrene were obtained from Aldrich Chemical Co. Inc. Octa(acetoxystyryl) octasilsesquioxane(AS-POSS) was synthesized as following method.
Synthesis of Octa(acetoxystyryl)octasilsesquioxane(AS-POSS)
Q8M8H (2.00 g, 1.96 m-mole) was placed in a 100 mL Schlenk flask equipped with a reflux condenser and a magnetic stirrer. Toluene (20 mL) was added to dissolve the cube, followed by the addition of 4-acetoxystyrene(3.2 g, 19.6 m-mole). Pt(dvs) (2 mM solution, 0.2ml) was added via a syringe. The reaction mixture was then heated to 80 under nitrogen and was complete℃ d in 4 hours. The solution was removed from Toluene under reduced pressure, then was dried in a vacuum oven at 80 for 24 ℃ hours. The product(3.17 g, 93 %), octa(acetoxystyryl)octasilsesquioxane (AS-POSS) was obtained. The AS-POSS is a colorless, viscous liquid, soluble in THF, CHCl3, acetone, etc.
Synthesis of Octa(phenol)octasilsesquioxane(octaphenol-POSS)
AS-POSS(3.17g, 1.82mmole) was placed in a 100ml Schlenk flask with a magnetic stirrer. THF(20ml) was added to dissolve the liquid, followed by NaOH(aq)(20ml, 10wt%). The reaction was carried out in room temperature under nitrogen and was complete in 2 days. Ethyl ether(20ml) and deionized water(20ml) was added to the solution, and then slowly added aqueous hydrochloric acid(10wt%) with stirring until pH=8. Two layers were formed. The top layer containing the product, octaphenol-POSS, was recovered. Residual ethyl ether and water were removed under vacuum. Octaphenol-POSS(2.26g, 65%) is a light brown, viscous liquid, soluble in THF, benzene, CHCl3, etc.
2.2 FTIR and NMR spectrum of the products
2.2.1 Characterizations
Nuclear magnetic resonance (1H NMR)
1H NMR spectra were recorded on a Varian Unity Inova 500 FT NMR Spectrometer
operating at 500 MHz with chemical shift reported in parts per million(ppm).
Deuterium chloroform was used as solvent.
Fourier Transform Infrared Spectroscopy (FTIR)
Infrared spectroscopic measurements were recorded on a Nicolet Avatar 320 FTIR spectrophotometer, and 32 scans were collected with a spectral resolution of 1 cm-1. Infrared spectra of polymer blend films were determined with the conventional NaCl disk method. All sample preparations were under continuous nitrogen flow to ensure minimal sample oxidation or degradation. Samples were prepared by casting the THF solution directly onto a NaCl disk and dried under conditions similar to those used in the bulk preparation.
2.2.2 Discussions
The FTIR spectra of Q8M8H, acetoxystyrene, and the final hydrosilylation product, AS-POSS, are shown in Figure 2-1. The strong absorption peak at 1100 cm-1 of Q8M8H and AS-POSS is the vibration of the siloxane (Si-O-Si) group, the feature of the POSS. The characteristic stretching vibration peaks of vinyl (φ-CH=CH2) and
Si-H groups are at 1650 and 2200 cm-1, respectively. In AS-POSS, the peaks for Si-H and the vinyl groups have disappeared completely, indicating that the complete reaction was obtained. Furthermore, the carbonyl group at 1765 cm-1 of acetoxystyrene remained in AS-POSS, is another evidence of the successful attachment of the acetoxystyrene on the POSS. In octaphenol-POSS, the broad band
of hydroxyl group appeared at 3400 cm-1 and the sharp peak of cabonyl group at 1765 cm-1 disappeared, indicated that the hydrolysis reaction is completed. Figure 2-2 and 2-3 shows the 1H NMR spectra of the AS-POSS and octaphenol-POSS, respectively.
Clearly, the peaks for the chemical shifts of vinyl protons around 5.8 ppm and the Si-H protons at 4.7 ppm are both disappeared, also indicating the complete reaction.
The vinyl groups of acetoxystyrene is able to attach the Si-H bond of Q8M8H on either α or βcarbon, therefore, the spectrum shown in Figure 2-2 and 2-3 are the mixture
of these two possible structures. From the integrated areas of these two methyl groups attach on Si, it is able to estimate that the ratio of the integrated areas of carbon 1:1’ is approximately 3:1. That means the α carbon attachment is three times of the β carbon attachment.
4000 3500 3000 2500 2000 1500 1000 500 Octaphenol-POSS
-O H
C =O
C =C
Si-H
AS-POSS
4-acetoxystyrene Q8M8H
W avenum ber (cm
-1)
Fig. 2-1. FTIR spectrum of the synthesis process
10 8 6 4 2 0
Fig. 2-2. NMR spectrum of AS-POSS
10 8 6 4 2 0
Fig. 2-3. NMR spectrum of octaphenol-POSS
Chapter 3 Studies of hydrogen bonding in Blends of Phenolic resin with AS-POSS
Abstract
We have successfully synthesized a polyhedral oligomeric silisesquioxane
(POSS) containing eight acetoxystyryl functional groups [octa(acetoxystyryl)- octasilsesquioxane (AS-POSS)] and then blends with the phenolic resin to form nanocomposites through the hydrogen bonding interaction between the phenolic hydroxyl group and the AS-POSS carbonyl group. Infrared spectroscopy analyses provide positive evidence for this type of hydrogen-bonding interaction. In addition, the inter-association equilibrium constant based on Painter-Coleman association model (PCAM) between phenolic resin and POSS can be indirectly calculated from the fraction of hydrogen-bonded carbonyl groups and quantitative analyses show that the hydroxyl-siloxane inter-association from PCAM is exactly consistent with the classical Coggeshall and Saier (C&S) methodology.
3.1 Introduction
Incorporation of nanoparticles into polymer matrixes to enhance polymer properties has attracted enormous interests in recent years due to its potential as candidate materials for bridging the gap between polymer and nanoparticles. In particular, polyhedral oligomeric silsesquioxanes (POSS) offer one solution to this need since they embody an inorganic-organic hybrid architecture with a well-defined inorganic framework composed of silicone and oxygen (SiO1.5)x and organic substituents containing nonreactive or reactive functionalities. By designing the functionality of the organic substituents, it is possible to create octafunctional or monofunctional macromonomers at desired usage. Therefore, these nanostructured chemicals can be incorporated easily into polymer chains through copolymerization, such as polysiloxane [1], poly(methyl methylacrylate) [2-3], poly(styrene) [4], epoxy [5], polyurethane [6], polyimide [7], and polynorborbornene [8].
Physical properties of polymer/POSS nanocomposites are strongly influenced by the miscibility between the host polymer and the POSS moiety. Random copolymerization by the organic functional groups of the POSS is one approach to attain this end. Therefore, in our previous study [9], we have synthesized a series of
poly(vinylphenol-co-vinylpyrrolidone-co-POSS) (PVPh-co-PVP-co-POSS) copolymers, resulting in significant glass transition temperature increase than the
corresponding non-POSS PVPh-co-PVP copolymer due to the strong hydrogen bonding existing between the PVPh and the POSS. The synthesis of a random copolymer is more complicated and time-consuming than a blend. Therefore, polymer blending is a more convenient method to prepare the polymer/POSS nanocomposites.
Since the combined entropy contribution to the free energy in mixing two polymers is negligibly small, specific intermolecular interactions are generally required for the miscibility of polymer blends. To improve the properties and miscibility of hybrid materials, it is necessary to ensure that favorable specific interactions exist between these components, such as hydrogen bonding [10], dipole–dipole interactions, and acid–base complexation.
Our previous study [11], indicated that a simple blending of POSS containing
nonreactive or inert diluent functional groups (here is octaisobutyl POSS) with phenolic resin did not give satisfactory results because of poor miscibility. The inter-association equilibrium constant between the phenolic hydroxyl group and the octaisobutyl POSS siloxane group (38.6) is lower than the self-association equilibrium constant of the pure phenolic (52.3) based on the Painter-Coleman association model (PCAM) [10]. This result indicates that the POSS tends to partial miscible with phenolic in the phenolic/POSS hybrid due to poor interaction between the phenolic resin and the octaisobutyl POSS. Functionalization of the POSS to
possess hydrogen bonding acceptor pedant groups is expected to improve the miscibility with phenolic resin. Functionalization of Q8M8H [HsiMe2OsiO1.5]8 can be achieved by the hydrosilylation reaction of Si-H groups in the presence of a platinum catalyst with acetoxystyrene. The hydrogen bonding interaction between the carbonyl group of the poly(acetoxystyrene) (PAS) and the hydroxyl group of the phenolic resin has widely investigated via infrared and solid state NMR in our previous studies [12].
We found that the inter-association equilibrium constant for the phenolic/PAS blend (64.6) is higher than the self-association equilibrium constant of pure phenolic (52.3), implying that the tendency toward hydrogen bonding of the phenolic resin and PAS dominates the self-association (intra-hydrogen bonding) of the phenolic resin in the mixture.
By infrared (FTIR) spectroscopy, the carbonyl, hydroxyl and siloxane vibration have been proved to be the excellent tool to detect these molecular interactions [13].
This tool can be used to study the mechanism of interpolymer miscibility through the formation of different type hydrogen bonds both qualitatively and quantitatively.
However, the inter-association equilibrium constant between the phenolic hydroxyl group and the POSS siloxane group can not be quantified directly because no carbonyl group is available to measure the fraction of the hydrogen bonded group from IR analysis in this binary blend. The siloxane-stretching mode near 1100-1200
cm-1 is a highly coupled mode that is conformationally sensitive and can not be readily decomposed into two peaks, corresponding to the free and the hydrogen-bonded siloxane absorptions. Therefore, according to our previous study [11], the inter-association equilibrium constant (KA) between hydroxyl group of phenolic resin and siloxane group of octaisobutyl POSS was calculated by using classical Coggeshall and Saier (C&S) [14] methodology. However, the inter-association equilibrium constant obtained from low molecular weight compound is not exactly the same as that from the true polymer blend due to the intramolecular screening and functional group accessibility effects in the miscible polymer blend [15].
Fortunately, in our previous study [11], the octaisobutyl POSS is the low molecular weight compound, thus this calculation can be considered as the true inter-association equilibrium constant between the phenolic hydroxyl group and the POSS siloxane group. To recheck the inter-association equilibrium constant between the phenolic hydroxyl group and the POSS siloxane group in the present study, the KA value is determined indirectly from a least square fitting procedure of the experimental fraction of hydrogen bonded carbonyl group of the AS-POSS in this binary blend. We found that the inter-association equilibrium constant of hydroxyl-siloxane have good correlation between these two methods. The hydrogen bonding formation is shown as scheme 3-1.
3.2 Experiment section
Scheme 3-1. Hydrogen bonding formation of blends of phenolic and AS-POSS
Materials
The phenolic used in this study was synthesized with sulfuric acid via a condensation reaction and gave average weights of Mn=500 and Mw=1200.
Octa(acetoxystyryl) octasilsesquioxane(AS-POSS) was synthesized as mentioned before..
Blend Preparation
Blends of phenolic/AS-POSS of various compositions were prepared by solution blending. Tetrahydrofuran solution containing 5 wt% of the mixture was stirred for 6-8 h, and then the solvent was evaporated slowly at room temperature for 1 day. To ensure total elimination of solvent, the powder of the blend was then dried in a vacuum oven at 60 for 2 days.℃
3.3 Results and Discussion
In our previous study [11], we have discussed in details the hydrogen bonding interaction between the phenolic hydroxyl groups and the POSS siloxane groups using 1D and 2D FTIR spectra. Figure 3-1(a) shows the infrared spectra in the range from 2700 cm-1 to 4000 cm-1 of the pure phenolic and various phenolic/AS-POSS nanocomposites measured at room temperature. The pure phenolic polymer exhibits two bands in the hydroxyl stretching region of the infrared spectrum. A very broad band centered at 3350 cm-1 is attributed to the wide distribution of the hydrogen bonded hydroxyl group while a narrower shoulder band at 3525cm-1 is caused by the free hydroxyl group. Figure 3-1(a) clearly shows that the intensity of the free hydroxyl absorption (3525cm-1) decreases gradually as the AS-POSS content of the blend is increased from 5 to 90 wt%. The hydrogen-bonded hydroxyl band in the
phenolic tends to shift into a higher frequency with increasing AS-POSS content at the vicinity of 3465 cm-1. This change is due to the switch from the hydroxyl-hydroxyl bond to the hydroxyl-carbonyl or hydroxyl-siloxane bond.
Figure 3-1(b) displays the infrared spectra in the region from 1680 cm-1 to 1820 cm-1 for various phenolic/AS-POSS blend compositions measured at room temperature. The carbonyl stretching frequency is split into two bands at 1760 cm-1 and 1735 cm-1, corresponding to the free and the hydrogen-bonded carbonyl groups, respectively. The band can be easily decomposed into two Gaussian peaks, with areas corresponding to the hydrogen-bonded carbonyl (1735cm-1) and free carbonyl (1760cm-1) as shown in Figure 3-2. In order to obtain the fraction of the hydrogen-bonded carbonyl, the known absorptivity ratio for hydrogen bonded and free carbonyl contributions is required. We have employed a value of αHB/αF=1.5,
which was previously calculated by Moskala et al. [10]. Fractions of hydrogen bonded carbonyl through curve fitting are summarized in Table 3-1, indicating that the hydrogen bonded fraction of the carbonyl group increases with the increase of the phenolic content.
Table 3-1: Curve fitting of the area fractions of the carbonyl stretching bands in the FTIR spectra of phenolic/AS-POSS blends recorded at room temperature.
ν: wavenumber, W1/2: half width, *fb: fraction of hydrogen bonding interaction
Free C=O H-Bonding C=O
Phenolic/AS-POSS
Wt Ratio ν, cmP–1P
WB1/2B, cmP–1P
ABfB % ν, cmP–1P
WB1/2B, cmP–1P
ABb B% fBbPB*P
0/100 1763.2 23.5 100 - - - -
10/90 1765.2 18.2 52.6 1739.3 29.3 47.4 37.5 20/80 1764.8 16.5 41.5 1737.3 28.0 58.5 48.4 30/70 1764.5 17.0 36.1 1735.5 27.8 63.9 54.1 40/60 1763.4 16.3 32.6 1733.5 26.3 67.4 58.0 50/50 1763.6 16.9 29.9 1733.6 26.3 70.1 61.0 70/30 1762.8 17.0 25.6 1732.1 25.5 74.4 66.0 80/20 1762.1 18.0 23.3 1731.3 24.7 76.7 68.8 90/10 1762.5 18.6 22.1 1731.0 25.3 77.9 70.1
4 0 0 0 3 8 0 0 3 6 0 0 3 4 0 0 3 2 0 0 3 0 0 0 2 8 0 0
Fig. 3-1 Infrared spectra of phenolic/AS-POSS blend at room temperature in the hydroxyl stretching region (a) and carbonyl stretching region (b).
1 8 0 0 1 7 7 0 1 7 4 0 1 7 1 0 1 6 8 0
Fig. 3-2 Deconstructed models of the carbonyl stretching bands (in Figure 2) of the weight percent of phenolic/AS-POSS blends at various compositions.
0 20 40 60 80 100 0.0
0.2 0.4 0.6 0.8 1.0
KA=38.6
Kc=26.0 KC=64.6
f HB
C=O
Phenolic Content (wt%)
Fig. 3-3 Fraction of the hydrogen-bonded carbonyl group versus composition:
(■)FT-IR data, (--) theoretical values from phenolic/PAS blend (KA=64.6) and (－) theoretical values from phenolic/AS-POSS (KA=26.0)
Figure 3-3 shows plots of the experimental data and theoretical predicted curve as a function of composition at room temperature that demonstrates the ability of PCAM to predict the degree of hydrogen bonding on the carbonyl group. Figure 3-3 indicates that the experimental values are generally lower than the predicted values based on using KA = 64.6 from phenolic/PAS blends. This result also indicates that the hydroxyl groups of phenolic not only interact with the carbonyl group of the acetoxystyrene but also with the siloxane group of the POSS, which is consistent with results from our previous study [11]. In other words, the AS carbonyl competes with
the siloxane of POSS to form a hydrogen bond with hydroxyl groups of the phenolic resin. The numerical method is employed to determine KA of the phenolic/AS-POSS blend according to the PCAM based on the fraction of the hydrogen bonded carbonyl group. The approximate equations are [11]:
⎥⎦
Where ΦA and ΦB denote volume fractions of non-self associated species A (AS-POSS) and self associating species B (phenolic), respectively. ΦA1 andΦB1 are
the corresponding volume fractions of the isolated AS-POSS and phenolic segments, respectively. r is the ratio of molar volume, VA/VB. Self-association equilibrium constants, KB and K2, describe the formation of multimers and dimers, respectively.
Finally, the KA is the equilibrium constant describing the association of A with B. In addition, KB and K2 are 23.3 and 52.3 at 25℃ of the pure phenolic [11]. In order to
calculate the inter-association constants (KA), the methodology of a least square method has been described in our previous study [12]. Table 3-2 lists all the
parameters required by the Painter-Coleman association model to estimate thermodynamic properties for this phenolic/AS-POSS blend. The inter-association equilibrium constant of 26.0 is obtained for the phenolic/AS-POSS blend. However, the KA=64.6 for the phenolic/PAS blend, implying that the KA between the hydroxyl group of phenolic and the siloxane group of POSS is equal to 38.6 (64.6-26.0 = 38.6), which is exactly consistent with the previously reported value based on the classical Coggeshall and Saier (C&S) methodology. Therefore, the inter-association equilibrium constant of hydroxyl-siloxane has good correlation between these two methods.
Table 3-2: Summary of the self-association and inter-association equilibrium constants and thermodynamic parameter of phenolic/AS-POSS blends at 25℃
Polymer V Mw Equilibrium Constant
K2 KB KA
Phenolic1 84 105 23.3 52.3
PAS2 128.6 162.2 64.6
8-isobutyl POSS3 778.6 872.2 38.6
AS-POSS 2058.6 2305.6 26.0
V: Molar Volume (ml/mol), Mw: Molecular Weight (g/mol), K2: Dimmer self-association equilibrium constant, KB: Multimer self-association equilibrium constant, KA: Inter-association equilibrium constant, 1: reference 11, 2: reference 12, 3: reference 11.
3.4 Conclusion
A new nanomaterial based on AS-POSS has been synthesized and the hydrogen bonding interaction of phenolic/AS has been investigated by using FTIR analyses.
The inter-association equilibrium constant between the hydroxyl group of the phenolic and the siloxane group of the POSS is determined indirectly from a least square fitting procedure based on the experimental fraction of hydrogen bonded carbonyl group in this blend system. The observed KA (38.6) of hydroxyl-siloxane is found equal to the value from classical classical Coggeshall and Saier (C&S) methodology.
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Chapter 4. A Novolac type of phenolic nanocomposite from octaphenol-POSS
Abstract
By adding the octaphenol-POSS before the polymerization process (which we
called the reaction system) of phenolic resin to join the reaction with phenol and
called the reaction system) of phenolic resin to join the reaction with phenol and