Synthesis of poly(ethylene oxide)-block-poly(methyl methacrylate)-block-polystyrene triblock copolymers by two-step atom transfer radical polymerization

The synthesis of ABC triblock copolymer poly(ethylene oxide)-block-poly(methyl methacrylate)-block-polystyrene (PEO-b-PMMA-b-PS) via atom transfer radical polymerization (ATRP) is reported. First, a PEO-Br macroinitiator was synthesized by esterification of PEO with 2-bromoisobutyryl bromide, which was subsequently used in the preparation of halo-terminated poly(ethylene oxide)-block-poly(methyl methacrylate) (PEO-b-PMMA) diblock copolymers under ATRP conditions. Then PEO-b-PMMA-b-PS triblock copolymer was synthesized by ATRP of styrene using PEO-b-PMMA as a macroinitiator. The structures and molecular characteristics of the PEO-b-PMMA-b-PS triblock copolymers were studied by FT-IR, GPC and ¹H NMR.     

Stereoregular poly(alkyl methacrylate)s: polymer-polymer and copolymer-polymer blends

Amorphous blends of isotactic and syndiotactic poly(methyl methacrylate) were found to be compatible. To evaluate the interaction between these tactic polymers, random copolymers of isotactic poly(methyl/ethyl methacrylate) were blended with syndiotactic poly(methyl methacrylate). Only the copolymers with an ethyl methacrylate content below 45% were compatible with syndiotactic poly(methyl methacrylate). Using a Flory-Huggins type treatment of copolymer mixtures, the segmental interaction parameters for poly(methyl methacrylate) with poly(ethyl methacrylate) and for isotactic with syndiotactic poly(methyl methacrylate) were calculated. The interaction parameter for the tactic poly(methyl methacrylate) pair was found to be small and negative.     

Role of intermolecular interaction between hydrophobic blocks in block-selected inclusion complexation of amphiphilic poly(ethylene oxide)-poly[(R)-3-hydroxybutyrate]-poly(ethylene oxide) triblock copolymers with cyclodextrins

The influence of hydrophobic interaction between poly[(R)-3-hydroxybutyrate] blocks on block-selected inclusion complexation between amphiphilic poly(ethylene oxide)-poly[(R)-3-hydroxybutyrate]-poly(ethylene oxide)) (PEO-PHB-PEO) triblock copolymers and α-cyclodextrin (α-CD) or γ-cyclodextrin (γ-CD) was studied by X-ray diffraction, differential scanning calorimetry (DSC), FTIR and ¹H NMR. Due to the stronger hydrophobic interaction at higher temperature, the amphiphilic triblock copolymer tends to aggregate to form tighter core-shell sphere with PHB block in the core and PEO in the corona. Therefore, the CD threaded onto PEO blocks cannot further slide onto the PHB block, which resulted in a highly block-selected inclusion complex formation. Moreover, the DSC results indicated that the triblock copolymer coalesced from its ICs with hot water showed an increase in microphase separation compared with the as-synthesized triblock copolymer, which further supports our hypothesis that CD only selectively includes PEO blocks of the triblock copolymer at higher temperature.     

Miscibility of C60-end-capped poly(ethylene oxide) with poly(vinyl chloride)

The miscibility of blends of single [60]fullerene (C₆₀)-end-capped poly(ethylene oxide) (FPEO) or double C₆₀-end-capped poly(ethylene oxide) (FPEOF) with poly(vinyl chloride) (PVC) has been studied. Similar to poly(ethylene oxide) (PEO), both FPEO and FPEOF are also miscible with PVC over the entire composition range. X-ray photoelectron spectroscopy showed the development of a new low-binding-energy Cl2p doublet and a new high-binding-energy O1s peak in FPEO/PVC blends. The results show that the miscibility between FPEO and PVC arises from hydrogen bonding interaction between the α-hydrogen of PVC and the ether oxygen of FPEO. From the melting point depression of PEO, FPEO or FPEOF in the blends, the Flory-Huggins interaction parameters were found to be −0.169, −0.142, −0.093 for PVC/PEO, PVC/FPEO and PVC/FPEOF, respectively, demonstrating that all the three blend systems are miscible in the melt. However, the incorporation of C₆₀ slightly impairs the interaction between PEO and PVC.     

Crystalline structures in ultrathin poly(ethylene oxide)/poly(methyl methacrylate) blend films

Amorphous poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) blend films in extremely constrained states are meta-stable and phase separation of fractal-like branched patterns happens in them due to heterogeneously nucleated PEO crystallization by diffusion-limited aggregation. The crystalline branches are viewed flat-on with PEO chains oriented normal to the substrate surface, upon increasing PMMA content the branch width remains invariant but thickness increases. It is revealed that PMMA imposes different effects on PEO crystallization, i.e. the length and thickness of branches, depending on the film composition.     

ABA triblock copolymers with two crystallizable blocks

Triblock copolymers of the ABA type were synthesized in which the A block is poly(ethylene oxide) (PEO), having molecular weight of 1000 or 2000, and the B block is poly(dimethylsiloxane) (PDMS), having molecular weight of about 8000 or 10,000. When the triblock copolymer was cooled from the melt, the PEO block crystallized at around room temperature. Upon further cooling to liquid nitrogen temperature and reheating, the crystallization of the PDMS middle block took place at around ?90°C. The melting temperatures and degrees of crystallinity of the PEO blocks in the copolymers were depressed from their respective pure state values. On the other hand, the melting points of the PDMS middle blocks in the copolymers were the same as the pure state values; furthermore, the degrees of crystallinity were unexpectedly much higher. © 1993 John Wiley & Sons, Inc.     

Effect of tacticity of poly(methyl methacrylate) on the miscibility with poly(vinyl pyrrolidone)

Isotactic, atactic, and syndiotactic poly(methyl methacrylates) (PMMA) (designated iPMMA, aPMMA, and sPMMA) with approximately the same molecular weight were mixed separately with poly(vinyl pyrrolidone) (PVP) primarily in chloroform to make three polymer blend systems. Differential scanning calorimetry (DSC) was used to study the miscibility of these blends. The results showed that the tacticity of PMMA has a definite impact on its miscibility with PVP. The aPMMA/PVP and sPMMA/PVP blends were found to be miscible because all the prepared films showed composition-dependent glass-transition temperatures (T_g). The glass-transition temperatures of the aPMMA/PVP blends are equal to or lower than weight average and can be qualitatively described by the Gordon–Taylor equation. The glass-transition temperatures of the other miscible blends (i.e., sPMMA/PVP blends) are mostly higher than weight average and can be approximately fitted by the simplified Kwei equation. The iPMMA/PVP blends were found to be immiscible or partially miscible based on the observation of two glass-transition temperatures. The immiscibility is probably attributable to a stronger interaction among isotactic MMA segments because its ordination and molecular packing contribute to form a rigid domain. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3190–3197, 2001     

Effect of tacticity of poly(methyl methacrylate) on the miscibility with poly(styrene‐co‐acrylonitrile)

Isotactic, atactic, and syndiotactic poly(methyl methacrylates) (PMMAs) (designated as iPMMA, aPMMA, and sPMMA) with approximately the same molecular weight were mixed separately with poly(styrene‐co‐acrylonitrile) (abbreviated as PSAN) containing 25 wt % of acrylonitrile in tetrahydrofuran to make three polymer blend systems. Differential scanning calorimetry (DSC) was used to study the miscibility of these blends. The results showed that the tacticity of PMMA has a definite impact on its miscibility with PSAN. The aPMMA/PSAN and sPMMA/PSAN blends were found to be miscible because all the prepared films were transparent and showed composition dependent glass transition temperatures (T_gs). The glass transition temperatures of the two miscible blends were fitted well by the Fox equation, and no broadening of the glass transition regions was observed. The iPMMA/PSAN blends were found to be immiscible, because most of the cast films were translucent and had two glass transition temperatures. Through the use of a simple binary interaction model, the following comments can be drawn. The isotactic MMA segments seemed to interact differently with styrene and with acrylonitrile segments from atactic or syndiotactic MMA segments. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2894–2899, 1999     

Measurement of the unperturbed dimensions of stereoregular poly(methyl methacrylate)

The results of measurements of unperturbed dimensions for a series of stereoregular poly(methyl methacrylates) are reported. The measurements were made by a recently developed method involving a gel permeation chromatograph coupled with an on-line low angle laser light scattering photometer. Measurements were performed in a thermodynamically good solvent, tetrahydrofuran at 25°C. The unperturbed dimensions were obtained by means of viscosity plots. Comparison of the results obtained by this method with those currently available in the literature, as well as with values predicted by statistical calculations, show good agreement. It was determined that a measurable difference occurs in the Mark-Houwink relationship between isotactic and syndiotactic poly(methyl methacrylate); isotactic poly(methyl methacrylate) is 30% more extended than syndiotactic poly(methyl methacrylate) in its unperturbed state; and isotactic poly(methyl methacrylate) exhibits a smaller degree of polymer solvent interaction than the syndiotactic form.     

Configurational effects on the crystalline morphology and amorphous phase behavior in poly(3‐hydroxybutyrate) blends with tactic poly(methyl methacrylate)

Poly(3‐hydroxybutyrate) (PHB) blends with two tactic poly(methyl methacrylate)s [PMMAs; isotactic poly(methyl methacrylate) (iPMMA) and syndiotactic poly(methyl methacrylate) (sPMMA)], being chiral/tactic polymer pairs, were investigated with regard to their crystalline spherulite patterns, optical birefringence, and amorphous phase behavior with polarized optical microscopy and differential scanning calorimetry. The PHB/sPMMA and PHB/iPMMA blends exhibited upper critical solution temperatures of about 225 and 240°C, respectively, on the basis of the results of thermal analysis and phase morphology. The interactions of two constituents in the blends (PHB/iPMMA or PHB/sPMMA) were measured to be insignificantly different for the PHB/sPMMA and PHB/iPMMA blends. However, syndiotacticity in PMMA exerted a prominent effect on the alteration of the PHB spherulite morphology, whereas, by contrast, isotacticity in PMMA had almost no effect at all. At high sPMMA contents (e.g., 30 wt %) in the PHB/sPMMA blend, the spherulites were all negatively birefringent and ringless when they were crystallized at any crystallization temperature between 50 and 90°C. That is, not only was the original ring‐banded pattern in the neat PHB spherulites completely disrupted, but the optical sign was also reverted completely from positively to negatively birefringent in the sPMMA/PHB blend; this was not observed in the iPMMA/PHB one. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

An all ATRP route to PMMA-PEO-PS and PMAA-PEO-PS miktoarm ABC star terpolymer

An all Atom Transfer Radical Polymerization (ATRP) route to synthesize miktoarm ABC star terpolymer, μ-(poly(methyl methacrylate)-poly(ethylene oxide)-polystyrene) (μ-(PMMA-PEO-PS)), was demonstrated. Poly(methyl methacrylate) (PMMA) with a halide end group was first prepared by ATRP of MMA. It was then activated under ATRP conditions at 30 °C to add a styrenic-terminated PEO macromonomer, resulting in the formation of PMMA-b-PEO. Finally, the active halide at the junction point of the diblock copolymer was used to initiate the ATRP of St at higher temperature. By a similar approach, μ-(poly(phenyl methacrylate)-poly(ethylene oxide)-polystyrene) (μ-(PhMA-PEO-PS)) was synthesized, hydrolysis of which in basic medium gave μ-(PMAA-PEO-PS). The polymers were characterized by ¹H NMR spectroscopy and gel permeation chromatography.     

Probing the structure of polymer blends by vibrational spectroscopy: the case of poly(ethylene oxide) and poly(methyl methacrylate) blends

The blends of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) are prepared in the form of thin films from solution casting. The Fourier transform infrared spectra of the blends are recorded in the spectral range 400–4000 cm^?1. The spectra are analysed using various recent techniques of vibrational spectroscopy. It is concluded that upon blending PEO takes preferentially a planar zig-zag structure. Furthermore the intermolecular interactions between the molecules of PEO and PMMA in blends are very weak and their compatibility as blends is more ‘physical’ than ‘chemical’. Further, on the basis of the atomic charges transferred from model molecules it is seen that the blending is preferred with isotactic PMMA when compared to syndiotactic PMMA.     

Comparison of Poly(Ethylene Oxide) Melt Crystallization in Blend and Block Copolymer Systems with Poly (Methyl Methacrylate) and Poly (Tert-Butyl Methacrylate)

DSC investigations are reported for a broad assortment of blends and copolymers of the immiscible poly(ethylene oxide) (PEO)/poly(tert-butyl) methacrylate) (PTBMA) system. Contrary to expectations, the PEO crystallization and melting behavior of the copolymer system is similar to that of the PEO/poly(methyl methacrylate) (PMMA) copolymer system (which is usually considered to be miscible in the melt). This is discussed with the concept of a UCST-type granulated demixing in the latter. In both systems the crystallization is rather sensitive to the block structure, even for comparable molecular weights and compositions. This indicates some importance of DSC as an additional tool in copolymer characterization. Free PEO ends favor the crystallization in all cases.     

Orientation relaxation study on poly(ethylene oxide)-poly(vinyl phenol) blends by polarization modulation infrared linear dichroism

Orientation relaxation in miscible poly(vinyl phenol) (PVPh)-poly(ethylene oxide) (PEO) blends (from 25 to 40 wt% PEO) was investigated using polarization modulation infrared linear dichroism. This blend was selected to study the effect of strong hydrogen bonds on relaxation. The results show that PEO is more oriented than PVPh, and remains so throughout the experimental relaxation time. Relaxation proceeds in three stages. PVPh relaxation is systematically faster than that of PEO, while PEO relaxation times increase steadily with increasing PEO content. For PVPh, a maximum in relaxation times is observed around 30 wt% PEO. Relaxation coupling occurs for concentrations in PEO lower than 30 wt%, is marginal for the 35 wt% and clearly absent for the 40 wt% PEO blend. By comparison with previous rheology and near-infrared data, it can be concluded that hydrogen bonds do not automatically insure cooperativity during relaxation: for cooperativity to occur, the minor component of the blend must interact preferentially with the major component. This is the case of PVPh-rich compositions, but not for PEO-rich compositions (for 35 and 40 wt% PEO), for which the minor PVPh constituent interacts strongly with both PEO and other PVPh chains.     

Blends of bacterial poly(3-hydroxybutyrate) and a poly(epichlorohydrin-co-ethylene oxide) copolymer: thermal and CO2 transport properties

In this work the miscibility and the carbon dioxide transport properties of a bacterial, isotactic poly(3-hydroxybutyrate) (iPHB) and its blends with a copolymer of epichlorohydrin and ethylene oxide (ECH-co-EO) have been studied. Blends were prepared by solution/precipitation. The aim to obtain miscible blends of iPHB with a rubbery second component (such as the ECH-co-EO copolymer) is to have mixtures with glass transition temperatures below room temperature. In these conditions, the iPHB chains not involved in the crystalline regions retain its mobility. This mobility seems to be necessary for the attack of microorganisms and the corresponding biodegradability.Miscibility is the general rule of these mixtures, as shown by the existence of a single glass transition temperature for each blend and by the depression of the iPHB melting point. The interaction energy density stabilising the mixtures, calculated using the Nishi-Wang treatment, was similar to those of other polymer mixtures involving different polyesters and poly(epichlorohydrin) (PECH) and ECH-co-EO copolymers. The so-called binary interaction model has been used in order to simulate the evolution of the interaction energy density with the ECH-co-EO copolymer composition. Previously reported experimental data on blends of iPHB with PECH and poly(ethylene oxide) (PEO) have been used to quantify the required segmental interaction energy densities.In the determination of the CO₂ transport properties of the mixtures, only iPHB rich blends containing up to 40% of copolymer were considered. The effect of the ECH-co-EO copolymer is to increase the sorption and the diffusion of the penetrant (and, consequently, the permeability) with respect to the values of the pure iPHB. This is primarily due to the reduction of the global crystallinity of the blends and to the low barrier character of the ECH-co-EO copolymer. Sorption data can be reasonably reproduced using an extension of the Henry's law to ternary systems.     

Preparation of highly syndiotactic block copolymers of methyl methacrylate and lauryl methacrylate and their characterization

Summary Highly syndiotactic diblock and triblock copolymers comprising lauryl methacrylate (LMA) and methyl methacrylate (MMA) with narrow molecular weight distributions were prepared by the living anionic polymerization with t-C₄H₉Li/(C₂H₅)₃Al in toluene at low temperature. The block copolymers were soluble in acetone which is a non-solvent for poly(lauryl methacrylate) (PLMA). ¹HNMR and vapor pressure osmometric analyses of the block copolymers indicated the aggregation of the copolymer in acetone through the interaction between PLMA blocks. Stereocomplex formation between the triblock copolymer and isotactic poly(methyl methacrylate) (PMMA) took place more effectively in solution than in the solid state.     

Influence of the tacticity of poly(methyl methacrylate) on the miscibility with poly(vinyl chloride)

It can be concluded from the work of Schurer et al.¹⁰ that poly(vinyl chloride) (PVC) is more miscible with syndiotactic than with isotactic poly(methyl methacrylate) (PMMA). By choosing different molar masses for the various tactic forms of PMMA it is possible to obtain blends with PVC with similar phase behaviour, i.e. in all cases a cloud-point curve with a minimum in the vicinity of 190°C. In this way a more quantitative statement about the influence of the tacticity of PMMA on its miscibility with PVC can be made. One of the principal differences between syndiotactic or atactic PMMA and isotactic PMMA is the higher flexibility of the latter. Using Flory's equation of state theory it will be shown that the effect of this difference is large enough to explain the difference in phase behaviour observed. Heats of mixing of low molar mass analogues were also measured and found to be negative.     

Isothermal crystallization kinetics of poly(ethylene terephthalate)-poly(ethylene oxide) segmented copolymer with two crystallizing blocks

The isothermal crystallization kinetics and morphology of poly(ethylene terephthalate)-poly(ethylene oxide) (PET30-PEO6) segmented copolymer, and poly(ethylene terephthalate) (PET) and poly(ethylene oxide) (PEO) homopolymers have been studied by means of differential scanning calorimetry (DSC) and a transmission electron microscope (TEM). It is found that the nucleation mechanism and growth dimension of PEO in the copolymer are different from that in the homopolymer, which is attributed to the effect of the crystallizability of PET-blocks. Furthermore, the crystallization rate of PEO-blocks in the copolymer is slower than that in the homopolymer because the PET-blocks phase is always partially solidified at the temperatures when PEO-blocks begin to crystallize. In contrast, the isothermal crystallization rate of PET-blocks in the copolymer is faster than that in the homopolymer because the lower glass transition temperature of the PEO-blocks (soft blocks) increases the mobility of the PET-blocks in the copolymer.     

Preparation of stereoregular block copolymer comprising isotactic PMMA and polyisobutylene blocks and its characterization

Summary A triblock copolymer of isotactic(it)-poly(methyl methacrylate) (PMMA) and polyisobutylene (PIB), it-PMMA-block-PIB-block-it-PMMA, was prepared by anionic polymerization of triphenylmethyl methacrylate initiated with , -dilithiated PIB diisobutyrate in tetrahydrofuran at -78°C, and subsequntt hydrolysis and methylation with diazomethane. Molecular weight distribution of the triblock copolymer was narrow, and the stereoregularity of the PMMA block was highly isotactic. Proton spin-lattice relaxation times of the block copolymer in acetone-d₆, which is non-solvent for PIB but dissolves the block copolymer, indicate the aggregation of the copolymer through PIB block. Stereocomplex formation between the it-block copolymer and syndiotactic(st)-PMMA-block-PIB-block-st-PMMA was also studied.     

Miscibility studies of binary and ternary mixtures of tactic poly(methyl methacrylates) with poly(vinylidene chloride‐co‐acrylonitrile)

Isotactic, atactic, and syndiotactic poly(methyl methacrylates) (i, a, and s PMMAs) were mixed with poly(vinylidene chloride‐co‐acrylonitrile) (Saran F) separately in tetrahydrofuran to make three polymer blend systems. Differential scanning calorimetry (DSC) was used mainly to study the miscibility of these blends. iPMMA and aPMMA were found to be miscible with Saran F based on the transparency and a single glass transition temperature (T_g) of the films. However, sPMMA was immiscible with Saran F because of the observation of two T_gs and opacity in most compositions of the blend. aPMMA is known to be miscible with sPMMA. Therefore aPMMA is both miscible with Saran F and sPMMA but Saran F and sPMMA are immiscible. Preliminary results of the effect of adding of aPMMA to immiscible sPMMA and Saran F mixtures were also reported. First, binary mixtures of atactic and syndiotactic PMMAs were also prepared and confirmed to be miscible. Elevation of T_g of the aPMMA/sPMMA blend above weight average was observed probably due to stereocomplexation occurred between aPMMA and sPMMA. Then ternary blends of atactic and syndiotactic PMMAs and Saran F in the weight ratios of about 3/1/4, 2/2/4, and 1/3/4 were also measured calorimetrically. A single T_g was observed for these three compositions different from two T_gs detected in the sPMMA/Saran F (50.0/50.0, i.e., 4/4) blend. Obviously, the composition of Saran was fixed in the ternary blends. When the other half of the blends was changing from pure sPMMA to sPMMA and aPMMA mixture, the blends became miscible because of the addition of aPMMA. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1313–1321, 2000