230 Acta Chim. Slov. 2005, 52, 230–237 Scientific Paper Semi-Interpenetrating Polymer Networks with Varying Mass Ratios of Functional Urethane and Methacrylate Prepoljmers1 Alojz Anžlovar* and Majda Žigon National Institute of Chemistry, Hajdrihova 19, SI-1000, Ljubljana, Slovenia, E-mail: alojz.anzlovar@ki.si Received 25-05-2005 t Dedicated to the memory of Prof. Dr. Tatjana Malavašič Abstract The morphology and mechanical properties of grafted semi-interpenetrating polymer netvvorks (SIPNs), based on ester-urethane (PU) prepolymers and methacrylate (PM) prepolymers were studied with regard to the PU and PM mass ratio and with regard to the concentration of functional groups. The SEM micrographs, glass transition temperature shifts of the individual constituents and mechanical properties of the studied SIPNs show that their miscibility is enhanced by the interaction of complementary functional groups which also stabilize the mixture at elevated temperatures. Hovvever, enhanced miscibility was observed only in SIPNs with PU component in excess, while in SIPNs with the PM component in excess miscibility was poor. Enhanced miscibility in the SIPN with functional groups having a PU/PM mass ratio of 0.5/0.5 was ascribed to the most intense interaction betvveen functional groups at this PU/PM ratio. Mechanical properties (Young’s modulus and tensile strength) of SIPN films were defined by the polymer component forming the matrix. They were significantly influenced by the interaction betvveen functional groups. Key words: semi-interpenetrating polymer netvvorks, functionalization of polvmers, morphology, mechanical properties, DSC, electron microscopy Introduction Interpenetrating polymer networks (IPNs), composed of two or more different crosslinked polymers, are relatively new engineering materials. They have been among the fastest growing areas in the field of blends during the past twenty years.1 Interpenetrating polymerization represents an innovative approach to solving the problem of polymer incompatibility. IPNs are defined as blends of two or more polymer netvvorks where at least one polymer component is prepared or crosslinked in the immediate presence of others.24 Besides ideal or Ml IPNs, in which both components are crosslinked independenth/ of each other, there are also other types of IPNs such as semi-IPNs or grafted-IPNs. Semi-IPNs have only one component cross-linked, while grafted-IPNs have covalent cross-links between both networks. There are a variety of combinations possible with these materials resulting in a broad range of properties. The performance of IPNs is determined by the physical and chemical nature of the constitutive networks, the relative proportion of components, the physical interactions between constitutive netvvorks, the IPN preparation procedure, and so on.5'6 When IPNs are used as materials for coating applications they cannot be prepared by conventional routes (sequential and simultaneous interpenetrating polymerization) due to the presence of volatile monomers. To avoid this problem IPNs are prepared from preformed prepolymers containing complementary functional groups that enhance their miscibility.712 In order to enhance the miscibility of urethane (PU) and methacrylate (PM) functional prepolymers we incorporated tertiary amine functional groups into the PM prepolymers and carboxylic functional groups into the hard segments of the PU prepolymers In our previous work we used PU prepolymers with polyether soft segments,1314 while later on PU with polyester soft segments were used. In the recent publication15 we reported on the morphology and mechanical properties of SIPNs based on ester PU and PM prepolymers with the mass ratio of 0.5/0.5 and their dependence on the concentration of functional groups. The best compatibility of polymer components in blends is in many cases found at mass ratios different to the equal Anžlovar and Žigon Functional Urethane and Methacrylate Prepolymers Acta Chim. Slov. 2005, 52, 230–237 231 mass ratio of components therefore the present work the mass ratio of PU and PM functional prepolymers focuses on the morphology and mechanical properties containing either no functional groups or 0.45 mmol of of the same type of SIPNs and their dependence on functional groups per g of polymer. MIXTURE OF PU AND PM PU PREPOLYMER \ CH3 HO— R — OCONH— R, — NHCOO — CH2 —C —CH2 — OCONH 3 1 INTERACTION BETVVEEN FUNCTIONAL GROUPS O H H3CN j CH3 N NHCOO (CH2)4 OH CROSS-LINKING WITH DDA PM COPOLYMER \ (CH2)2 O CO ( CH2 C CH2 C CH2 C CH2 C CH2 C CH2 C )m COOCH3 CH3 COOCH3 CH3 COOCH3 CH3 CH3 CH3 COOCH3 CH3 OH (CH2)2 O CO H I °-x /° C / I / NHCOO— R, —OCONH— R — NHCOO - CH2 — C —CH2 — OCONH— R„ — NHCOO—(CH2)4 — OCONH O 1 1 CH3 CH3 NHCOO— R, —OCONH— R — NHCOO —CH2 — C —CH2 — OCONH— R„ — NHCOO—(CH2)4 — OCONH O 1 1 o O I FORMATION OF GRAFTED - SIPN H3CX ,CH3 N (CH2)2 O OCONH I (CH2)2 CO O ( CH2 C CH2 C CH2 C CH2 C CH2 C CH2 C )m CH3 CO CH3 COCCH3 CH3 I I I I I I I CCOCH3 CH3 lili CCOCH3 CH3 COOCH3 CH3 LEGEND: H3C..CH3 R = 1 CH2 H3C -(CH2)6 9 (CH2)6 - R = 2 N N ONo I R = 3 OO ((CH2)5 C O) (CH2)4 (OC(CH2)5 ) nn (CH2)6 — Figure 1. The scheme of preparation of SIPNs from polyester PU and PM prepolymers with functional groups. Anžlovar and Žigon Functional Urethane and Methacrylate Prepolymers R O R 2 R 2 R 2 H 232 Acta Chim. Slov. 2005, 52, 230–237 Table 1. The number-average molecular weights - Mn of PU and PM prepolymers as measured by SEC. PU prepolymer Cone. of funct. groups (mmol/g) M„ (g/mol) PM prepolymer Cone, of funet. groups (mmol/g) M„ PUp-0 0.00 12300 PMp-0 0.00 11200 PUp-45______________________045____________________5300___________PMp-45__________________0A5________________10700 Experimental Synthesis of prepolymers PU prepolymers without any, and with 0.45 mmol of carboxylic funetional groups per g of polymer (PUp-0 and PUp-45) were synthesized aceording to prepolymer procedure deseribed by Tirpak et al.16 using isophoronediisocyanate (IPDI), polycaprolactone (PCL), Mn =2000, and 1,4-butanediol (BD) as monomers, and dibutyl tin dilaurate (DBTDL) as the catalyst. 2,2’-Bis-(hydroxymethyl) propionic acid (DMPA) was used as a funetional comonomer to introduce carboxylic funetional groups into the PUp-45 prepolymer. The molar ratio of OH/NCO groups was 1.05/1. PM prepolymers with zero and 0.45 mmol of tertiary amine funetional groups per g of polymer were synthesized by radical chain pofymerization in solution (ethyl methyl ketone - MEK, reaction temperature = 80 °C) from methyl methacrylate (MMA) and hydroxyethyl methacrylate (HEMA)1315 (0.038 mmol/g of polymer). Ar,Ar-dimethylaminoethyl methacrylate (DMAEMA) was used as a funetional comonomer to introduce tertiary amine groups into the PMp-45 prepofymer. AIBN was used as an initiator and dodecylmercaptane as a regulator of the molecular weight. The PM prepofymer contains a small concentration of OH groups, therefore some covalent bonds are likely to be formed betvveen PU and PM components. In the studied system the concentration of OH groups is constant, consequently grafting could not be the cause of the observed changes in thermal and mechanical properties of the samples studied. For simplification purposes, the term “SIPN” will be used herein to refer to grafted-SIPNs. The samples of PU and PM prepofymer were designated as PUp - X or PMp - X, where X is the concentration of funetional groups in 10"5 mol/g of polymer. Preparation of SIPNs SIPNs in the form of thin films (thickness was approximately 50 |a,m) were prepared from prepofymer solutions in MEK. The prepofymers were mixed in a glass vessel under a constant flow of dry nitrogen in a given mass ratio of PU and PM prepofymer. The cross-linking agent [l,3,5-isocyanatohexamethylene triisocyanate, Desmodur-DA, (DDA)] was admixed in a 100% excess to the calculated amounts of OH groups in both prepofymers. The films were čast at 60 °C or at 110 °C, then kept at 60 °C for 2h and finally at 85 °C for 16h. The solvent evaporated within a few minutes at 60 °C, and in less than a minute at 110 °C. The SIPN samples were designated as IPN - X/Y, where X is the concentration of funetional groups in the PU and PM prepolymers (10-5 mol/g of pofymer) and Y is the mass fraetion of the PM component. Two series of SIPN samples with funetional group concentrations of 0 and 0.45 mmol/g (designation IPN - 0 and IPN - 45) were prepared. The chemical struetures of prepofymers and SIPNs studied are given in Figure 1. Methods Size Exclusion Chromatographv (SEC) The molecular weight averages of PM and PU prepolymers were determined by SEC at 25 °C on a Perkin-Elmer liquid chromatograph consisting of a LC-250 pump, a LC-30 differential refraetometer and a PL-gel Mixed D (5|a,m) column with a precolumn. THF was used as the eluent (flow rate lmL/min). The columns were calibrated using PMMA standards for PM prepolymers and using PS standards for PU prepolymers. The results of the analysis are given in Table 1. Differential Scanning Calorimetrv (DSC) The glass transition temperatures (Tg) and changes in heat capacities (Acp) during glass transition were determined in the temperature range from -80 °C to 130 °C. Samples were dried prior to this at 50 °C in a vacuum overnight. The measurements were performed on a Perkin-Elmer DSC-7 with a heating rate of 20 °C/min after holding the samples at -80 °C for 10 minutes. Glass transition temperatures of pure PU and PM prepofymers and the corresponding SIPNs were determined from thermograms, and their shifts in SIPNs were calculated. Conclusions about the miscibility and morphology were made on the basis of Tg shifts in SIPNs. The Karasz-Couchman1719 equation (1) was used for calculation of the theoretical values of glass transitions of SIPNs, assuming an ideal miscibility of PU and PM prepofymers: , coiAcpi\n Tgi + aiAcpiln Tgi In Tgc = ------------------------------------------------- (1) coiAcpi + coiAcpi Anžlovar and Žigon Funetional Urethane and Methacrylate Prepolymers Acta Chim. Slov. 2005, 52, 230–237 233 where a>1 and u>2 are the mass fractions of components, Tgl and Tg2 are their glass transition temperatures, Acpl and Acp2 are the heat capacity differences for components 1 and 2 during glass transition, respectively, and Tgc is the glass transition temperature of the mixture. Mechanical Properties Mechanical properties (tensile strength, elongation at break, Young’s modulus) were measured according to the ASTM D 882-75b standard using an Instron 1022 dynamometer at a speed of 1 mm/min and with an initial grip separation of 100 mm. Hardness of thin films was determined by Koenig’s method (DIN 53157). Scanning Electron Microscopy (SEM) Samples broken on the dynamometer were coated twice with gold, and micrographs of the fractured surfaces were taken using a JEOL JSM 840 A microscope operating at an acceleration voltage of 15 keV (magnification 1000x) in secondary electron emission mode. Results and Discussion SEM micrographs of the IPN-0 and IPN-45 series with different mass ratios of PU and PM components are shown in Figure 2. The phase separation is much more pronounced in SIPNs with no functional Figure 2. SEM micrographs (magnif. - 1000x) of IPNs cast at 60 °C with no functional groups (IPN 0, PU/PM = a) 0.7/0.3, c) 0.5/0.5, e) 0.3/0.7) and with 0.45 mmol/g of functional groups (IPN-45, PU/PM = b) 0.7/0.3, d) 0.5/0.5, f) 0.3/0.7). Anžlovar and Žigon Functional Urethane and Methacrylate Prepolymers 234 Acta Chim. Slov. 2005, 52, 230–237 groups (IPN-0, Figure 2 a,c,e) than in SIPNs with functional groups (IPN-45, Figure 2 b,d,f), which show relatively homogenous morphologies. Comparing the micrographs of IPN-45 series with different PU/PM mass ratios it can be observed that phase separation is reduced, if one component is in excess, especially when it is the PU component that is in large excess (Figure 2b). Differences in morphologies lead to the conclusions that functional groups substantially improve the compatibility of PU and PM prepolymers and that SIPNs with very homogeneous morphologies can be obtained, when the PU component is in excess. Glass transition temperatures as a function of the PU and PM prepolymer mass ratio of the IPN-0 and IPN-45 series čast at 60 °C are shown in Figure 3. Comparison of the Tg values of PU soft segments and of PM component for IPN-45 and for IPN-0 samples with theoretical values calculated using Karasz-Couchman equation shows that SIPN samples of both series can be divided into three groups. 120 100 80 60 40 20 0 -20 o o m oi U U U vj fl^i A * " ¦ ¦ , - -¦ ¦ A t t li -A" ¦A" 'A A A 0.2 0.4 0.6 0.8 Mass fraction of PM component Figure 3. Glass transition temperatures of PU soft segments and PM component in IPN samples with no functional groups (IPN 0) and with 0.45 mmol/g of functional groups (IPN 45) čast at 60 °C in dependence of the PU/PM mass ratio: IPN 0 - (PU soft s. -(A), PM comp. -(O)); IPN 45 - (PU soft s. -(¦), PM comp. -(¦)); calculated values by the equation 1: IPN 0 (—), IPN 45 (—). The first group are SIPN samples with the PU component in excess. In these samples, where PU forms the matrix, we observe shifts in the Tg values of the PU soft segments towards higher temperatures. Shifts are observed in the IPN-45 and IPN-0 series, and Tg values are close to the values calculated using the Karasz-Couchman equation, thus indicating enhanced miscibility of the PU and PM component in both series, although enhancement is more pronounced in the IPN-45 series. Comparing these Tg shifts with those of the polyether PU soft segments in SIPNs, it is evident that PU prepolymers with polyester soft segments are more compatible with PM prepolymer than with polyether ones.13 Better compatibility of polyester PU soft segments in the SIPNs is caused by the increased intensity of interaction (increased number of hydrogen bonds) due to the presence of a polar ester carbonyl group.20'2 The glass transitions of the PM component could not be observed in these SIPN samples. Our explanation for this phenomenon is that glass transition temperatures are shifted to lower temperatures and are hidden in intense glass transitions of the PU soft segments. The second group are SIPN samples with the PM component in excess. The glass transition temperatures of the PM component were observed in these samples but they shifted to slightly lower or higher temperatures compared to the pure PM. Most of these changes are within the range of experimental error indicating that at least a part of the PM component is not interpenetrated with the PU component. Glass transition temperatures of PU soft segments are 20 to 40 °C lower than the values calculated using the Karasz-Couchman equation. This indicates the poor miscibility of components in SIPNs where the PM component forms a matrix. The third group are IPN-0 and IPN-45 samples with equal mass ratios of PU and PM prepolymers. Here we observe different shifts in Tg of PU soft segments in IPN-0 and in IPN-45 samples compared to the calculated values. The glass transition temperature of the IPN-0/0.5 is 12 °C lower than the calculated value while the measured value of the IPN-45/0.5 is close to the calculated one, thus indicating enhanced miscibility. Glass transition temperature shifts of the PM component are shifted slightly towards higher or lower temperatures compared to Tg values of the pure PM. These shifts are in the range of experimental error and it can be therefore inferred that a part of the PM component is not interpenetrated with PU chains. This was observed also at other IPN systems.6 Shifts in the Tg of PU soft segments clearly indicate enhanced miscibility in the IPN-45/0.5 sample and poor miscibility in the IPN-0/0.5 sample, thereby confirming that functional groups do enhance the miscibility of the components. The compatibilizing effect of functional groups is most highly expressed at an equal mass ratio of PU and PM components because functional groups are in an equimolar ratio and therefore interaction betvveen functional groups is the most intense at this mass ratio of PU and PM component. Films of SIPN samples were prepared also by casting the MEK solution at 110 °C, which substantially reduces the solvent evaporation time. The main difference betvveen the glass transition temperatures of PU soft segments of the IPN-0 and IPN-45 samples čast at both temperatures is shown in Figure 4. While Tg values of PU soft segments of the IPN-45 samples do not show any important differences, there is a major difference in Tg shifts of PU soft segments betvveen IPN-0 samples čast at 60 and those at 110 °C. Tg values of the IPN-0 samples čast at 60 °C shift to higher temperatures 0 Anžlovar and Žigon Functional Urethane and Methacrylate Prepolymers Acta Chim. Slov. 2005, 52, 230–237 235 with the increased mass ratio of the PM component, while the Tg values in IPN-0 samples čast at 110 °C are practically independent of the mass ratio of components thus indicating their phase separation and poor miscibility of the components. Phase separation is most probably the consequence of the reduced viscosity of the mixture at elevated temperatures. In the IPN-45 series the mixture is stabilized by the interaction betvveen the functional groups22 and in these samples phase separation is substantially reduced. A similar conclusion was also drawn from the polarizing micrography and WAXD data. It was found in the IPN-45/0.5 that this interaction prevented ordering of domains in the PU component.23 50 i 40 30 20 10; 0 -10 -20 -30 ^o^o* t 0 0.2 0.4 0.6 0.8 1 PM prepolymer mass fraction Figure 4. Glass transition temperatures of PU soft segments in IPN samples dependent on the mass ratio of the PU and PM component: IPN-0 series čast at 60 °C (O) and at 110 °C (A), IPN-45 series čast at 60 °C (D) and at 110 °C (O). In general, glass transition temperatures of the PM component seem to be independent of the concentration of functional groups and the mass ratio of both components, while Tg shifts of PU soft segments indicate enhanced miscibility of components, if the PU component forms a matrix or if the mass ratios of both components are equal. The fact that Tg values of the PM component remain practically the same does not necessarily mean that the miscibility of the components in the SIPN samples is poor. Namely, ESR studies of the IPN-45/0.5 sample confirmed that PM chains are partially plasticised by the PU component,23 indicating an enhanced miscibility in this sample. The observed anomaly in glass transition temperatures of the PM component can be ascribed to: - the compensation of the plasticising effect of the PU component by the interaction betvveen functional groups acting as physical cross-linking.24 Chemical cross-linking may be an additional contribution to this. Physical and chemical crosslinking shifts the temperature of the glass transition towards higher temperatures,2529 - the structure of the PM prepofymer - tertiary amine functional groups are built into side chains creating steric hindrance and preventing the PM main chain from coming into close contact with the main chain of the PU prepofymer,30 - non-random distribution of functional groups along polymer chains of prepolymers due to the segmented structure of the PU prepofymer and due to nonideal copolymerisation reaction of the PM prepolymer.15 The mechanical properties of SIPNs with different mass ratios of the PU/PM prepofymer without (IPN-0 series) and with functional groups (IPN-45 series) are given in Table 2 and Figure 5. Only SIPN films čast at 60 °C were suitable for testing mechanical properties, since those čast at 110 °C contained bubbles formed by the fast evaporation of the solvent. Mechanical properties of SIPN films were primarify defined by the polymer component in excess that forms the matrix. This is seen from the substantial drop of the elongation and from the substantial increase of the Young’s modulus in the region of the equal mass ratios of components in both series where phase inversion takes plače31 (Table 2, Figure 5). Nevertheless, the same results show some important differences betvveen IPN-0 and IPN-45 series. The tensile strength of the IPN-0 samples is lower than that of the pure PU prepolymer (PUp-0), while the tensile strength of the IPN-45 samples increases up to a PU/PM mass ratio 0.5/0.5 (Table 2) and then rapidly deteriorates. The Young’s moduli of SIPNs without functional groups are much lower than those of SIPNs with functional groups. In the IPN - 0 series the dependence of Young’s modulus on the mass fraction of the PM component is sigmoidal, indicating phase inversion in the steep slope of the curve (PU/PM mass ratio = 0.5/0.5), while in the IPN-45 series the modulus starts to increase at a PU/PM mass ratio of 0.7/0.3 and has a maximum at a ratio of 0.4/0.6 indicating that strong interactions are present at these PU/PM ratios (Figure 5). It can be concluded from these results that, by adding betvveen 40 and 50 mass % of the PM prepofymer to the PU component, the Young’s modulus can be substantially increased (Figure 5). However, 30 mass % or less PM does not so greatly change any of the mechanical properties (except Koenig’s hardness) of the SIPNs, when compared to the pure PU prepofymer. This can be important from the technological point of view because polyacrylates are much cheaper than polyurethanes. Koenig’s hardness as a function of composition (Figure 5) also differs betvveen the two series. The IPN-0 series has a typical sigmoidal shape, while the curve of the IPN-45 series starts to increase substantially from the pure PU component, reaches a maximum at PU/PM Anžlovar and Žigon Functional Urethane and Methacrylate Prepolymers 236 Acta Chim. Slov. 2005, 52, 230–237 Table 2. Tensile strength and elongation of films of IPN - 0 and IPN - 45 series with different PU/PM mass share ratios; films cast at 60 °C. PU/PM mass ratio in Tensile strength Elongation PU/PM mass ratio in Tensile strength Elongation IPN-0 (N/mm2) (%) IPN-45 (N/mm2) (%) 1.0/0.0 12.5 ± 1.4 492 ± 15 1.0/0.0 20.0 ± 2.10 380 ± 20 0.9/0.1 3.50 ± 1.2 350 ± 73 0.9/0.1 13.3 ± 0.84 358 ± 13 0.8/0.2 3.37 ± 0.57 332 ± 61 0.8/0.2 17.3 ± 1.53 347 ± 24 0.7/0.3 7.10 ± 2.0 365 ± 63 0.7/0.3 20.4 ± 1.36 302 ± 20 0.6/0.4 3.20 ± 0.32 202 ± 20 0.6/0.4 21.7± 1.10 248 ± 11 0.5/0.5 2.78 ± 0.52 37.5 ± 19 0.5/0.5 24.0 ± 1.05 86.7 ± 27 0.4/0.6 2.18± 0.25 5.9 ± 2.8 0.4/0.6 9.74 ± 5.2 1.6 ± 0.51 0.3/0.7 1.83 ± 0.26 2.3 ± 0.55 0.3/0.7 2.15± 0.9 0.79 ± 0.24 0.2/0.8 - - 0.2/0.8 - - 0.1/0.9 - - 0.1/0.9 - - PM component. The sample with an equal PU/PM mass ratio having 0.45 mmol of functional groups/g of polymer shows exceptional enhancement of miscibility due to an intense interaction between complementary functional groups which are in the equimolar ratio at this PU/PM mass ratio. Interaction betvveen functional groups also stabilizes the PU and PM prepolymer mkture at elevated temperatures (110 °C) and thus prevents the separation of components under these conditions. Mechanical properties of SIPN films in general were defined by the polymer component in excess and forming the matrix, although interaction betvveen functional groups also influenced their properties resulting in increased Young’s modules and tensile strengths compared to those without functional groups. Mechanical properties of SIPNs (Young’s modulus and Koenig's hardness) as a function of the PU/PM mass ratio supported conclusions about the enhanced compatibility of PU and PM prepolymers due to interaction betvveen functional groups. Acknowledgement The financial support of the Ministry of Higher Education, Science and Technology and the Slovenian Research Agency is gratefully acknowledged (program P2-0145-104). References 1. L. W. Barrett, L. H. Sper\ing, Trends Pofym. Sci. 1993,i, 45^9. 2. S. B. Pandit, V. M. Nadkarni, Macromolecules 1994, 27, 4583-4594. 3. S. B. Pandit, S. S. Kulkarni, V M. Nadkarni, Macromolecules 1994, 27, 4595-4604. 4. H. A. Al-Salah, H. X. Xiao, J. A. McLean, K C. Frisch, Polym. Int. 1992, 28, 323-327. 5. S. K. Das, S. Lenka,/. Appl. Polym. Sci. 2000, 75, 1487-1492. 6. R. Greco, M. Iavarone, A. Fiedlerova, E. Borsig, /. Macromol. Sci. Pure 2000, A37, 433-446. Anžlovar and Žigon Functional Urethane and Methacrylate Prepolymers 50 i 40 30 20 \ 10 0 -10 \ -20 -30 0 0.2 0.4 0.6 0.8 1 PM prepolymer mass fraction Figure 5. Young’s modulus of IPN - 0 (O) and IPN - 45 series (A) and Koenig’s hardness of IPN - 0 (V) and IPN - 45 series (D) as a function of the PM prepolymer mass fraction. mass ratio of 0.4/0.6 and then slightly decreases as the composition goes towards the pure PM component. This is the most pronounced difference in miscibility of PU and PM components betvveen the IPN-0 and IPN-45 series. Conclusions A study was made on the morphology and mechanical properties of SIPNs with different PU/PM mass ratios without (IPN-0) and with complementary functional groups at a concentration of 0.45 mmol/g (IPN-45) based on ester-urethane (PU) prepolymers with carboxylic groups and methacrylic (PM) prepolymers with tertiary amine functional groups. SEM micrographs and shifts in T showed enhancement of miscibility of PU and PM components in IPNs with high concentration of functional groups. According to the shifts in Tg and SEM micrographs of the IPN samples with differrent PU/PM mass ratios miscibility of components is enhanced in IPNs in which PU component forms the matrix while no enhancement was observed in IPNs in which matrix is formed by the Acta Chim. Slov. 2005, 52, 230–237 237 7. H. X. Xiao, K C. Frisch, H. L. Frisch,/. Polym. Sci. Pol. Chem. 1983, 21, 2547-2557. 8. H. X. Xiao, K C. Frisch, H. L. Frisch,/. Polym. Sci. Pol. Chem. 1984, 22, 1035-1042. 9. A. Patsis, H. X. 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C. Cesteros, E. Meaurio, I. Katime, Polymer 1995, 36, 2765-2775. 30. A. A. Lin, L. K. Kwei, A. Reiser, Macromolecules 1989, 22, 4112^-119. 31. D. Fox, R. Allen, Compatibility In: Encyclopaedia of Polymer Science and Engineering, H. F. Mark, N. N. Bikales, G. C. Overberger, G. Mengeš, J. I. Kroschvvitz, Editors. John Wiley & Sons, 1985, Vol. 3, pp. 758-775. Povzetek Sintetizirali smo ester-uretanske (PU) predpolimere z vgrajenimi karboksilnimi funkcionalnimi skupinami in polimetakrilatne (PM) predpolimere z vgrajenimi terciarnimi aminskimi funkcionalnimi skupinami in iz njih pripravili delno prepletene polimerne mreže (SIPN) pri različnih temperaturah. Študirali smo morfologijo in mehanske lastnosti SIPN v odvisnosti od koncentracije funkcionalnih skupin in od razmerja med predpolimeroma. Premiki temperature steklastega prehoda in SEM mikrografije kažejo povečanje mešjivosti PU in PM komponent zaradi interakcije med funkcionalnimi skupinami. V SIPN s presežkom PU komponente je mešljivost PU in PM predpolimera izboljšana, medtem ko v vzorcih SIPN s presežkom PM komponente predpolimera nista kompatibilna. Najboljša mešljivost komponent v SIPN je pri razmerju PU/PM = 0.5/0.5, ker so interakcije pri tem razmerju (ekvimolarno razmerje funkcionalnih skupin) najbolj intenzivne. Interakcije med funkcionalnimi skupinami vplivajo tudi na mehanske lastnosti SIPN, vendar pa njihove vrednosti v največji meri določa komponenta, ki tvori matrico. Anžlovar and Žigon Functional Urethane and Methacrylate Prepolymers