Study on thermal enhancement mechanism of POSS‐containing hybrid nanocomposites and relationship between thermal properties and their molecular structure

In this study, a series of poly(4‐acetoxystyrene) (PAS)‐octavinyl polyhedral oligomeric silsesquioxane (POSS) blends and the polystyrene (PS)‐octavinyl POSS blends were prepared by the solution‐blending method and characterized with Fourier transform infrared (FTIR), X‐ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) techniques. The results show that the glass‐transition temperature (T_g) of the PAS‐POSS blends increases at a relatively low POSS content and then decreases at a relatively high POSS content. POSS can effectively improve the thermal stability of the PAS‐POSS blends at low POSS content, and T_g of PAS‐POSS blends decreases with the increase in POSS content at relatively high POSS content. However, the T_g of the PS‐POSS blends persistently decreases even at very low POSS content. T_g change mechanism was investigated in detail by XRD, TEM, and FTIR spectra. The influence mechanism of POSS content and dispersion in composites, and parent polymer structure on thermal properties of the blends was investigated in detail. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Poly(vinyl pyrrolidone‐co‐octavinyl polyhedral oligomeric silsesquioxane) hybrid nanocomposites: Preparation,thermal properties,and Tg improvement mechanism

A series of poly(vinyl pyrrolidone‐co‐octavinyl polyhedral oligomeric silsesquioxanes) (PVP‐POSS) organic–inorganic hybrid nanocomposites containing different percentages of POSS were prepared via free radical polymerization and characterized by FTIR, high‐resolution ¹H‐NMR, solid‐state ²⁹Si‐NMR, GPC, DSC, and TGA. POSS contents in these nanocomposites can be effectively controlled by varying the POSS feed ratios which can be accurately quantified by FTIR curve calibration. On the basis of ²⁹Si‐NMR spectra, average numbers of reacted vinyl groups of each octavinyl‐POSS macromer are calculated to be 5–7, which depends on POSS feed ratios. Both GPC and DSC results indicate that these nanocomposites display network structure and the degree of crosslinking increases with the increase of the POSS content. The incorporation of POSS into PVP significantly improves their thermal properties (T_g and T_dec) primarily due to crosslinking structure and dipole–dipole interaction between POSS cores and PVP carbonyl groups. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of poly(HEMA‐co‐MMA)‐g‐POSS nanocomposites by combination of reversible addition fragmentation chain transfer polymerization and click chemistry

New hybrid poly(hydroxyethyl methacrylate‐co‐methyl methacrylate)‐g‐polyhedral oligosilsesquioxane [poly(HEMA‐co‐MMA)‐g‐POSS] nanocomposites were synthesized by the combination of reversible addition fragmentation chain transfer (RAFT) polymerization and click chemistry using a grafting to protocol. Initially, the random copolymer poly(HEMA‐co‐MMA) was prepared by RAFT polymerization of HEMA and MMA. Alkynyl side groups were introduced onto the polymeric backbones by esterification reaction between 4‐pentynoic acid and the hydroxyl groups on poly(HEMA‐co‐MMA). Azide‐substituted POSS (POSS? N₃) was prepared by the reaction of chloropropyl‐heptaisobutyl‐substituted POSS with NaN₃. The click reaction of poly(HEMA‐co‐MMA)‐alkyne and POSS? N₃ using CuBr/PMDEATA as a catalyst afforded poly(HEMA‐co‐MMA)‐g‐POSS. The structure of the organic/inorganic hybrid material was investigated by Fourier transformed infrared, ¹H‐NMR, and ²⁹Si‐NMR. The elemental mapping analysis of the hybrid using X‐ray photoelectron spectroscopy and EDX also suggest the formation of poly(HEMA‐co‐MMA)‐anchored POSS nanocomposites. The XRD spectrum of the nanocomposites gives evidence that the incorporation of POSS moiety leads to a hybrid physical structure. The morphological feature of the hybrid nanocomposites as captured by field emission scanning electron microscopy and transmission electron microscopic analyses indicate that a thick layer of polymer brushes was immobilized on the POSS cubic nanostructures. The gel permeation chromatography analysis of poly(HEMA‐co‐MMA) and poly(HEMA‐co‐MMA)‐g‐POSS further suggests the preparation of nanocomposites by the combination of RAFT and click chemistry. The thermogravimetric analysis revealed that the thermal property of the poly(HEMA‐co‐MMA) copolymer was significantly improved by the inclusion of POSS in the copolymer matrix. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Characterization of poly(vinyl pyrrolidone‐co‐isobutylstyryl polyhedral oligomeric silsesquioxane) nanocomposites

Poly(vinyl pyrrolidone‐co‐isobutyl styryl polyhedral oligomeric silsesquioxane)s (PVP–POSS) were synthesized by one‐step polymerization and characterized using FTIR, high‐resolution ¹H‐NMR, solid‐state ¹³C‐NMR, ²⁹Si‐NMR, GPC, and DSC. The POSS content can be controlled by varying the POSS feed ratio. The T_g of the PVP–POSS hybrid is influenced by three main factors: (1) a diluent role of the POSS in reducing the self‐association of the PVP; (2) a strong interaction between the POSS siloxane and the PVP carbonyl, and (3) physical aggregation of nanosized POSS. At a relatively low POSS content, the role as diluent dominates, resulting in a decrease in T_g. At a relatively high POSS content, the last two factors dominate and result in T_g increase of the PVP–POSS hybrid. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2208–2215, 2004     

Preparation and thermal property of hybrid nanocomposites by free radical copolymerization of styrene with octavinyl polyhedral oligomeric silsesquioxane

The poly(styrene‐co‐octavinyl‐polyhedral oligomeric silsesquioxane) (PS–POSS) organic–inorganic hybrid nanocomposites containing various percent of POSS were prepared via one‐step free radical polymerization and characterized by FTIR, high‐resolution ¹H NMR, ²⁹Si NMR, GPC, DSC, and TGA technologies. The POSS contents in these nanocomposites were determined using FTIR calibration curve. The result shows that the POSS contents in nanocomposites can be tailored by varying the POSS feed ratios. On the basis of the POSS contents in the nanocomposites and the ¹H NMR spectra, the number of reacted vinyl groups of each octavinyl‐POSS macromonomer were calculated to be 6–8. DSC and TGA measurements indicate that the incorporation of POSS into PS homopolymer can apparently improve the thermal properties of the polymeric materials. The dramatic T_g and T_dec increases are mainly due to the formation of star and low cross‐linking structure of the nanocomposites, where POSS cores behave as the joint points and hinder the motion and degradation of the polymeric chains. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis of PS‐g‐POSS hybrid graft copolymer by click coupling via ”graft onto” strategy

Polystyrene (PS)‐incorporated polyhedral oligomeric silsesquioxanes (POSS) organic–inorganic hybrid graft copolymer could be achieved by click coupling reaction between alkyne groups in POSS and azido groups in PS via “graft onto” strategy. Alkyne‐functionalized POSS was synthesized via thiol‐ene facile click reaction and subsequent amidation reaction with very high yield. Azido‐multifunctionalized PS could be synthesized by chloromethylation and subsequent azido reaction. The chemical structures of PS‐(CH₂Cl)_m, PS‐(CH₂N₃)_m, and PS‐g‐POSS were determined by Fourier transform infrared and ¹H NMR characterization. PS‐g‐POSS presented a better hydrophobic property with contact angle of 113° than that of PS (85°). And PS‐g‐POSS with ≤5% of grafting degree had lower glass transition temperature (T_g) than that of PS and then it increased up to 112°C with grafting degree. An obvious aggregation of POSS phase with 10–80 nm in size was formed in PS‐g‐POSS matrix. In addition, 5 wt % of PS‐g‐POSS was added to general purpose polystyrene (GPPS) to remarkably improve its tensile strength from 45 to 57 MPa. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Hybrid nanocomposites based on novolac resin and octa(phenethyl) polyhedral oligomeric silsesquioxanes (POSS): miscibility, specific interactions and thermomechanical properties

Hybrid nanocomposites were prepared via solution blending of octaphenethyl POSS into novolac resin. The resulted hybrid blends were investigated by Fourier-transformed infrared spectra (FTIR), polarized optical microscopy (POM), wide X-ray diffraction and differential scanning calorimetry (DSC). FTIR results showed that there existed intermolecular hydrogen bond between the hydroxyl groups of the phenolic resin and POSS siloxane groups, which could promote POSS to disperse well in the polymer matrix up to 20 wt% POSS loading. At higher POSS loading, POSS would aggregate and lead to macrophase separation, which was demonstrated by POM, DSC and WXRD. Finally, hexamethylene tetramine was used to cure the novolac blends to form hybrid network phenolic nanocomposites. Dynamic mechanical analysis results showed that the storage modulus of the hybrid networks was improved up to 20 wt% POSS loading; the T _g was increased with increasing POSS content and higher than that of the control phenolic resin except that 5 wt% POSS loading. Thermo gravimetric analysis showed that the thermal stability of hybrid networks was also enhanced with the incorporation of POSS.     

Novel phenyl‐POSS/polyurethane aqueous dispersions and their hybrid coatings

A facile and rapid preparation of 3‐(2‐aminoethylamino)propylheptaphenylPOSS (AA‐POSS), a special phenyl‐POSS that contains two functional amino groups (Scheme 1), is demonstrated by the corner‐capping method. Then AA‐POSS forms a series of novel phenyl‐POSS/PU aqueous dispersions. The structure of AA‐POSS has been confirmed by ¹H, ¹³C, ²⁹Si NMR, and ESI‐MS. The POSS/PU hybrid films are studied by Fourier transform infrared spectrometer (FT‐IR), gel permeation chromatography (GPC), scanning electron microscope (SEM), X‐ray diffraction (XRD) spectra, differential scanning calorimetry (DSC) analysis, and thermal gravimetric analyzer (TGA). FT‐IR and GPC are conducted to validate the chemical structure of the hybrid PU. The properties of hybrid films display significant changes with notable increases in T_g, thermal properties, tensile strength, as well as surface hydrophobicity. These changes are attributed to the incorporation of novel POSS into PU. Moreover, these significant material property enhancements are achieved at low levels of POSS incorporation (only 4%). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1611–1620, 2013     

Morphology of blends containing high concentrations of POSS nanoparticles in different polymer matrices

This article reports an investigation into the miscibility and morphology of octaisobutyl‐substituted polyhedral oligomeric silsesquioxane (ibPOSS) nanocages over a wide concentration range (25–75 wt%) in polymer matrices, produced by solution blending. Three different, strategically chosen polymers were used: polystyrene (PS), poly(isobutyl methacrylate) (PIBMA), and poly(methyl methacrylate) (PMMA), to allow the effect of matrix structure and polarity on miscibility to be investigated. Differential scanning calorimetry, dynamic mechanical analysis, X‐ray diffraction, and scanning electron microscopy were used to characterize the composite systems. The T_g of PMMA and PIBMA were found to increase with introduction of ibPOSS, whereas PS did not show any significant change of T_g with increasing POSS content, indicating differing degrees of interaction. The phase separation has been found and a cubic POSS crystal structure has been observed in all blends with different size. The glass transition increased with concentration, even though all compositions were predominantly phase‐separated, and we suggest that this is due to the influence of the external face of the crystalline units on the polymer chains, and possibly some polymer contained within the crystalline POSS phase. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Effect of PMMA addition on characterization and morphology of PVDF

Polyvinylidene fluoride and polymethylmethacrylate (PVDF/PMMA) films were blended with different concentrations by casting method. Structural, spectroscopic, and morphological characteristics of both the interface and the surface of the films have been investigated. The blends were characterized using X‐ray diffraction (XRD), Fourier transform infrared (FTIR), UV–visible, differential thermal analysis (DTA), and scanning electron microscopy (SEM). All measurements reveal that the blends take place based on the influence of PMMA content on PVDF. FTIR results indicate the possible interactions between carbonyl group of PMMA and CH₂ groups of PVDF which indicates the formation of blends. Optical absorption spectra suggested the presence of an optical gap (E_g) which decreased with increasing PMMA content. UV/VIS spectra were characterized by a sharp edge and a window of wavelength range 290–350 nm for some blends. The optical window can be used as an optical sensor or band pass filter. The degree of crystallinity was found to decrease with increasing PMMA content, which was confirmed by XRD and DTA analysis. SEM micrograph shows spherulites which increase with the addition of PMMA and it becomes sharper and contains a longitudinal shape. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Nanocomposites based on copolymers of fluorinated imide and polyhedral oligomeric silsesquioxane macromonomer: microstructure and morphology studies

Towards the development of copolymeric nanocomposites, N‐3(trifluoromethyl)phenyl‐7‐oxanorbornene‐5,6‐dicarboximide (TFI) monomer and a macromonomer of polyhedral oligomeric silsesquioxane (POSS) were synthesized. Ring‐opening metathesis polymerization to copolymerization of specified proportions of the two co‐monomers was carried out. All the monomers and polymers were characterized using Fourier transform IR analysis and ¹H and ²⁹Si NMR. Gel permeation chromatography shows that copolymeric nanocomposites have a lower average molar mass than a homopolymer of TFI (HTFI). TGA shows that the thermal stability of the copolymer is inversely proportional to the proportion of POSS units. DSC studies have demonstrated that the glass transition temperature (T_g) of a nanocomposite possessing 25 wt% POSS is at a higher temperature (180 °C) than that of HTFI (175 °C). Transmission electron microscopy and AFM images of copolymers are consistent with the self‐assembled spherical aggregation of POSS units, while X‐ray diffraction studies have confirmed the homogeneous dispersion of the same units within the nanocomposites. © 2012 Society of Chemical Industry     

Mechanical,thermal, and viscoelastic response of novel in situ CTBN/POSS/epoxy hybrid composite system

The present study focuses on the preparation of a novel hybrid epoxy nanocomposite with glycidyl polyhedral oligomeric silsesquioxane (POSS) as nanofiller, carboxyl terminated poly(acrylonitrile‐co‐butadiene) (CTBN) as modifying agent and diglycidyl ether of bisphenol A (DGEBA) as matrix polymer. The reaction between DGEBA, CTBN, and glycidyl POSS was carefully monitored and interpreted by using Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC). An exclusive mechanism of the reaction between the modifier, nanofiller, and the matrix is proposed herein, which attempts to explains the chemistry behind the formation of an intricate network between POSS, CTBN, and DGEBA. The mechanical properties, such as tensile strength, and fracture toughness, were also carefully examined. The fracture toughness increases for epoxy/CTBN, epoxy/POSS, and epoxy/CTBN/POSS hybrid systems with respect to neat epoxy, but for hybrid composites toughening capability of soft rubber particles is lost by the presence of POSS. Field emission scanning electron micrographs (FESEM) of fractured surfaces were examined to understand the toughening mechanism. The viscoelastic properties of epoxy/CTBN, epoxy/POSS, and epoxy/CTBN/POSS hybrid systems were analyzed using dynamic mechanical thermal analysis (DMTA). The storage modulus shows a complex behavior for the epoxy/POSS composites due to the existence of lower and higher crosslink density sites. However, the storage modulus of the epoxy phase decreases with the addition of soft CTBN phase. The T_g corresponding to epoxy‐rich phase was evident from the dynamic mechanical spectrum. For hybrid systems, the T_g is intermediate between the epoxy/rubber and epoxy/POSS systems. Finally, TGA (thermo gravimetric analysis) studies were employed to evaluate the thermal stability of prepared blends and composites. POLYM. COMPOS., 37:2109–2120, 2016. © 2015 Society of Plastics Engineers     

Organic base‐catalyzed sol–gel route to prepare PMMA–silica hybrid materials

A series of sol–gel‐derived organic–inorganic hybrid materials that comprise organic poly(methyl methacrylate) (PMMA) and inorganic silica (SiO₂) was successfully prepared using aniline as an organic base catalyst to catalyze the sol–gel reactions of tetraethylorthosilicate (TEOS). Aniline was adopted not only as a catalyst but also as a dispersing agent during the preparation of the hybrid materials. The as‐prepared hybrid materials were then characterized using transmission electron microscopy, SEM/energy dispersive X‐ray spectroscopy and Fourier transform infrared spectroscopy. The characteristic temperatures (including T_d and T_g) of the hybrid materials slightly exceeded those of neat PMMA, as revealed from thermogravimetric analysis and differential scanning calorimetry evaluations. Studies of the protection against corrosion demonstrated that the hybrid coatings all improved the protection performance on cold‐rolled steel coupons relative to that of neat PMMA coatings, according to measurements of electrochemical corrosion parameters. Additionally, incorporating silica particles into the polymer may effectively reduce the gas permeability of the polymer membrane. Reducing the size of silica particles (at the same silica feeding) further improved the gas barrier property. Optical clarity studies indicated that introducing silica particles into the PMMA matrix may slightly reduce the optical clarity of the films/membranes, as determined by UV‐visible transmission spectroscopy. The contact angle of H₂O of the hybrid films increased with the amount of aniline. Copyright © 2006 Society of Chemical Industry Society of Chemical Industry     

Development of novel biopolymer blends based on poly(l‐lactic acid), poly((R)‐3‐hydroxybutyrate), and plasticizer

Poly(l ‐lactic acid) (PLLA), a biopolymer that can be derived from renewable resources, is known for its brittleness as a result of slow crystallization rates under supercooling conditions, which is associated with the formation of large spherulites. In addition, the glass transition temperature (T_g) of PLLA is 60°C, such that the polymer chain is immobile at room temperature. These disadvantages make PLLA unsuitable for use in the food packaging sector. In this research, biopolymer blends based on PLLA and poly((R)‐3‐hydroxybutyrate) (PHB), together with tributyl citrate (TBC) as a plasticizer, were developed. TBC was added to increase polymer chain mobility, and to decrease PLLA T_g from 60 to 10°C in blends. Furthermore, the addition of PHB as a nucleating agent to PLLA resulted in an increased proportion of smaller spherulites. Fourier‐transform infrared (FT‐IR) spectroscopy indicated that the carbonyl group and several other characteristic peaks in blends are shifted to lower wavenumber. In addition, polarized optical microscopy experiments confirmed the results of differential scanning calorimetry, FT‐IR, and wide‐angle X‐ray diffraction, showing that PHB enhances the crystallization behavior by acting as a bionucleation. POLYM. ENG. SCI., 54:1394–1402, 2014. © 2013 Society of Plastics Engineers     

Surface‐initiated atom transfer radical polymerization from Mg(OH)2 nanoparticles to prepare the well‐defined polymer‐Mg(OH)2 nanocomposites

Well‐defined polymer‐Mg(OH)₂ nanocomposites were prepared by atom transfer radical polymerization (ATRP). The ATRP initiators were covalently attached to the Mg(OH)₂ by esterification of 2‐chloropropionyl chloride with hydroxyl group. The amount of polymer grafted from Mg(OH)₂ can be controlled using a different catalyst system and adding a small amount of polar solvent. The well‐defined diblock copolymer, consisting of poly(styrene) (PS) and poly(methyl methacrylate) (PMMA) were synthesized. The products were characterized by nuclear magnetic resonance, Fourier transform infrared, differential scanning calorimetry, and thermal gravimetric analysis. The morphologies of PS/PMMA and PS/PMMA/Mg(OH)₂‐g‐PS‐b‐PMMA blends are compared by using a scanning electron microscope. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3680–3687, 2007     

Synthesis and characterization of poly(methyl methacrylate)/montmorillonite nanocomposites by in situ bulk polymerization

Poly(methyl methacrylate)/montmorillonite (MMT) nanocomposites were prepared by in situ bulk polymerization. The results showed that the silicone coupling agent affected the structure and properties of hybrid materials. XRD analysis showed that the dispersion of clay in nanocomposites with silicone‐modified organophilic MMT was more ordered than that in nanocomposites with unmodified organophilic MMT. The glass transition temperature (T_g) of the nanocomposites was 6–15°C higher and the thermal decomposition temperature (T_d) was 100–120°C higher than those of pure PMMA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2256–2260, 2003     

Synthesis,structure, and properties of high‐impact polystyrene/octavinyl polyhedral oligomeric silsesquioxane nanocomposites

The organic–inorganic hybrid nanocomposites from high‐impact polystyrene/octavinyl polyhedral oligomeric silsesquioxane (HIPS/POSS) containing various percentages of POSS were prepared by free radical polymerization and characterized by Fourier transform infrared spectroscopy (FTIR), ¹H‐NMR, thermal gravity analysis (TGA), X‐ray diffraction (XRD), and transmission electron microscopy (TEM). The octavinyl POSS has formed covalent bond connected PS‐POSS hybrid with polystyrene. POSS can well disperse in the composites at the composition of 0.5 and 1 wt%. The mechanical properties and thermostability of HIPS/POSS nanocomposites were significantly improved. The tensile strength, the izod impact strength, and the elongation at break of the nanocomposite containing 1 wt% of POSS was increased, respectively, by 15.73%, 75.62%, and 72.71% in comparison with pristine HIPS. The thermal decomposition temperature of HIPS/POSS (1 wt% of POSS) was 33°C higher than that of pristine HIPS. The HIPS/POSS nanocomposites showed great potential for applications in many fields, such as electric appliance and automotive trim. POLYM. COMPOS. 37:1049–1055, 2016. © 2014 Society of Plastics Engineers     

Preparation and properties of polycarbonate nanocomposites using attapulgite grafted poly(methyl methacrylate) as a potential nanofiller

The Core‐shell hybrid particles with attapulgite (ATP) as the core and polymethylmethacrylate (PMMA) as the shell (ATP‐g‐PMMA) were prepared via reversible addition‐fragmentation chain transfer (RAFT) polymerization method. The diameter of ATP‐g‐PMMA was increased to 50–60 nm, and the surface hygroscopicity was decreased observably after surface grafting. Then, ATP‐g‐PMMA hybrid particles were filled into the polycarbonate (PC) by melt mixing to afford nanocomposites, and the mechanical properties, microstructures, thermal stability, and rheological behavior of nanocomposites were investigated by varying ATP‐g‐PMMA concentration in the range 1, 3, 5, and 7 wt % in PC. Fourier Transform infrared spectroscopy (FTIR) suggested that there is no esterification reaction between particles and matrix. Slight changes in tensile strength, and noticeable decrease of elongation and impact strength were observed with the increase in ATP‐g‐PMMA particles loading. The morphology evaluated by field‐emission scanning electron microscopy (FESEM) indicated that ATP‐g‐PMMA was dispersed with a diameter range of 80–100 nm, and phase separation was appeared with increasing ATP‐g‐PMMA loadings. Thermogravimetric analysis (TGA) results revealed the thermal stability of composites was strengthened. The disentanglement and interface slip induced by preferred orientation and directional arrangement of ATP‐g‐PMMA resulted in lower complex viscosity (η*) and higher loss factor (tan δ) compared with the pristine PC. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42262.     

Compatibility and properties of alternating ethylene-tetrafluoroethylene copolymer and poly(methyl methacrylate) blends

Blends of an alternating ethylene-tetrafluorethylene copolymer (ETFE) and poly(methyl methacrylate) (PMMA) were prepared by melt mixing in a mixer. Compatibility, thermal behaviour and morphology of the blends of various compositions were investigated by using dynamic mechanical analysis (d.m.a.), Fourier transform infra-red spectroscopy (FTi.r.), solid-state nuclear magnetic resonance (n.m.r.) spectroscopy, differential scanning calorimetry (d.s.c.) and wide-angle X-ray diffraction. D.m.a. and d.s.c. results show that the glass transition temperature (T_g) of the ETFE in the blends increases as the PMMA content increases and the T_g of the PMMA moves to low temperatures when the ETFE content increases. In addition, d.s.c. results indicate an additional T_g, which is located between the T_g of PMMA and that of ETFE. The presence of this additional T_g suggests the existence of one semicrystalline phase and two amorphous phases—an ETFE/PMMA phase and a PMMA-rich phase. D.s.c. results also indicate that the melting temperature of ETFE decreases while the crystallinity of ETFE increases slightly as the PMMA content increases. FTi.r. results show that the absorption peak of the carbonyl group of the PMMA in the blends stays almost at the same position as in the pure component. Solid-state n.m.r. results reveal that the changes in chemical shift of the carbonyl group of PMMA in the blends are less than 0.5 ppm. These results confirm that only weak interactions exist between ETFE and PMMA. X-ray diffraction results reveal that no new crystal forms appear in the blends. © 1997 Elsevier Science Ltd.     

Polymer blends of stereoregular poly(methyl methacrylate) and poly(styrene‐co‐p‐hydroxystyrene)

Isotactic, atactic, and syndiotactic poly(methyl methacrylates) (PMMAs) (designated as iPMMA, aPMMA, and sPMMA) were mixed with poly(styrene‐co‐p‐hydroxystyrene) (abbreviated as PHS) containing 15 mol % of hydroxystyrene separately in 2‐butanone to make three polymer blend systems. Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy were used to study the miscibility of these blends. The three polymer blends were found to be miscible, because all the prepared films were transparent and there was a single glass transition temperature (T_g) for each composition of the polymers. T_g elevation (above the additivity rule) is observed in all the three PMMA/PHS blends mainly because of hydrogen bonding. If less effective hydrogen bonding based on the FTIR evidence is assumed to infer less exothermic mixing, sPMMA may not be miscible with PHS over a broader range of conditions as iPMMA and aPMMA. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 431–440, 1999