Segmented copolymers of uniform tetra-amide units and poly(phenylene oxide): 1. Synthesis and thermal-mechanical properties

Copolymers of telechelic poly(2,6-dimethyl-1,4-phenylene ether) segments with terephthalic methyl ester endgroups (PPE-2T), 13 wt% crystallisable tetra-amide segments of uniform length (two-and-a-half repeating unit of nylon-6,T) and dodecanediol (C12) as an extender were made via a polycondensation reaction in the melt. The maximum reaction temperature was 280 °C. The PPE-2T/C12/T6T6T copolymers are semi-crystalline materials with a T_g around 170 °C, a melting temperature of 264-270 °C and a T_g/T_m ratio of above 0.8. The modulus is high up to the T_g, which is not achievable in a blend of PPE and polyamide. The most probable morphology is that of long crystalline nano-ribbons in the amorphous matrix. The materials are slightly transparent and have good solvent resistance, low water absorption and good processability.     

Segmented copolymers of uniform tetra-amide units and poly(phenylene oxide): 2. Crystallisation behaviour

The crystallisation behaviour of copolymers of telechelic poly(2,6-dimethyl-1,4-phenylene ether) segments with terephthalic methyl ester endgroups (PPE-2T), 13 wt% crystallisable tetra-amide segments of uniform length units (two-and-a-half repeating unit of nylon-6,T) and dodecanediol (C12) was studied. The crystallisation rate of the T6T6T units was found to be very high despite the high T_g/T_m ratio. The supercooling (T_m−T_c) as measured by DSC is 18 °C at a cooling rate of 20 °C/min. WAXD has elucidated that the tetra-amide units remain organised in the melt.     

Segmented copolymers of uniform tetra-amide units and poly(phenylene oxide). Part 4. Influence of the extender

Copolymers of telechelic poly(2,6-dimethyl-1,4-phenylene ether) (PPE) segments, uniform crystallisable tetra-amide units (T6T6T, 6-15 wt%) and different diols (C2-C36, polytetramethylene oxide) as an extender were synthesised. The telechelic PPE segment was end-functionalised with terephthalic ester groups and had a molecular weight of 3100 g/mol. The coupling between the PPE segment and the T6T6T unit was made with diols. The influence of the length and flexibility of the diol-extender and the concentration of the T6T6T units were studied on the thermal (DSC) and thermal-mechanical (DMA) properties of the copolymers. A crystalline T6T6T phase in the copolymers was evident from 9 wt% onwards. The length of diol extender had an effect on the glass transition temperature of the PPE phase, the crystallinity of the T6T6T segments and modulus above the glass transition temperature. With ethylene glycol the T_g of the copolymer was high but the crystallinity of the T6T6T rather low. With dodecanediol or hexanediol as an extender the T_gs of the PPE phase were somewhat lower, but the crystallinities of the T6T6T segments higher. With C36 and polytetramethylene oxide diols, the T_g were strongly decreased and broad and the modulus above the glass transition temperature not so high.     

Synthesis and characterisation of telechelic poly(2,6-dimethyl-1,4-phenylene ether) for copolymerisation

Telechelic poly(2,6-dimethyl-1,4-phenylene ether) (PPE) segments are interesting starting materials, for example for copolymerisation. A good method to make partly bifunctional PPE-2OH is by redistribution or depolymerisation of high molecular weight commercial PPE with tetramethyl bisphenol A. The product has a bimodal molecular weight distribution because only ∼70-80% of high molecular weight starting material is depolymerised. The phenolic endgroups can be modified easily by a fast and complete reaction with methyl chlorocarbonyl benzoate. The product after endgroup modification is called PPE-2T and has two terephthalic methyl ester endgroups and a molecular weight of 2000-4000 g/mol. The functionality of these PPE-2T products is around 1.8. The bimodal PPE-2OH and PPE-2T products can be separated in a high and low molecular weight fraction by selective precipitation. The low molecular weight fraction has a narrow molecular weight distribution with a polydispersity between 1.2 and 1.5.     

Segmented copolymers of poly(phenylene ether) and polyester

Copolymers of telechelic poly(2,6-dimethyl-1,4-phenylene ether) (PPE) segments with terephthalic methyl ester end groups (PPE-2T, 3500 g/mol) and poly(dodecane terephthalate) (PDDT) were made via a polycondensation reaction in the melt. The inherent viscosities of the segmented copolymers were high. The thermal properties of the copolymers were studied by DMA. The segmented block copolymers had a transparent melt at low (12 wt%) PDDT contents. The segmented block copolymers had at higher PDDT contents a non-transparent melt and two glass transition temperatures. The glass transition temperature of the PPE phase decreased strongly with PDDT content in the copolymer. The glass transition temperature of the PDDT phase increased moderately with PPE content. At low PPE contents the modulus of the PDDT increased strongly with increasing PPE content.     

Segmented copolymers of uniform tetra-amide units and poly(phenylene oxide): 3. Influence of tetra-amide content

Copolymers of telechelic poly(2,6-dimethyl-1,4-phenylene ether) (PPE) segments and crystallisable T6T6T units (two-and-a-half repeating unit of nylon-6,T) of uniform length were synthesised. The influence of the T6T6T content (0-20 wt%), the purity of the telechelic PPE and uniformity of the T6T6T segment length on the thermal mechanical (DMA) properties were studied. The polymers are semi-crystalline materials with a high T_g/T_m ratio of above 0.8. Increasing the T6T6T content (0-20 wt%) has little effect on the T_g transition region, but the modulus of the rubbery plateau increases strongly (0-13 MPa) and the flow temperature increases slightly as well (260-275 °C). The materials are transparent when the T6T6T content is below 10 wt%. Surprisingly copolymers based on telechelic PPE of narrow molecular weight distribution had lower crystallinity. The uniformity of the T6T6T segment length seems to have little effect on the properties of the copolymer, as long as at least 70% of the units are of one length.     

Segmented copolymers of uniform tetra‐amide units and poly(phenylene oxide) by direct coupling

Segmented copolymers with telechelic poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE) segments and crystallizable bisester tetra‐amide units (two‐and‐a‐half repeating unit of nylon‐6,T) were studied. The copolymers were synthesized by reacting bifunctional PPE with hydroxylic end groups with an average molecular weight of 3500 g/mol and bisester tetra‐amide units via an ester polycondensation reaction. The bisester tetra‐amide units had phenolic ester groups. By replacing part of the bisester tetra‐amide units with diphenyl terephthalate units (DPT), the concentration of tetra‐amide units in the copolymer was varied from 0 to 11 wt%. Polymers were also prepared from bifunctional PPE, DPT, and a diaminediamide (6T6‐diamine). The thermal and thermal mechanical properties were studied by DSC and DMA and compared with a copolymer with flexible spacer groups between the PPE and the T6T6T. The copolymers had a high T_g of 180–200°C and a melting temperature that increased with amide content of 220–265°C. The melting temperature was sharp with monodisperse amide segments. The T_m – T_c was 39°C, which suggests a fast, but not very fast, crystallization. The crystallinity of the amide was ～ 20%. The copolymers are semicrystalline materials with a high T_g and a high T_g/T_m ratio (> 0.8). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 512–518, 2007     

Ionene segmented block copolymers containing imidazolium cations: Structure-property relationships as a function of hard segment content

Imidazolium ionene segmented block copolymers were synthesized from 1,1′-(1,4-butanediyl)bis(imidazole) and 1,12-dibromododecane hard segments and 2000 g/mol PTMO dibromide soft segments. The polymeric structures were confirmed using ¹H NMR spectroscopy, and resonances associated with methylene spacers from 1,12-dibromododecane became more apparent as the hard segment content increased. TGA revealed thermal stabilities ≥250 °C for all imidazolium ionene segmented block copolymers. These ionene segmented block copolymers containing imidazolium cations showed evidence of microphase separation when the hard segment was 6-38 wt%. The thermal transitions found by DSC and DMA analysis found that the T_g and T_m of the PTMO segments were comparable to PTMO polymers, namely approximately −80 °C and 22 °C, respectively. In the absence of PTMO soft segments the T_g increased to 27 °C The crystallinity of the PTMO segments was further evidence of microphase separation and was particularly evident at 6, 9 and 20 wt% hard segment, as indicated in X-ray scattering. The periodicity of the microphase separation was well-defined at 20 and 38 wt% hard segment and found to be approximately 10.5 and 13.0 nm, respectively, for these ionenes wherein the PTMO soft segment is 2000 g/mol. Finally, the 38 and 100 wt% hard segment ionenes exhibited scattering from correlations within the hard segment on a length scale of approximately 2-2.3 nm. These new materials present structure on a variety of length scales and thereby provide various routes to controlling mechanical and transport properties.     

Polyether‐amide segmented copolymers based on ethylene terephthalamide units of uniform length

Segmented copolymers were synthesized using the crystallizable bisesterdiamide segment (N,N′‐bis(p‐carbomethoxybenzoyl)ethanediamine) T2T‐dimethyl (a one‐and‐a‐half repeating unit of nylon 2,T) and poly(tetramethyleneoxide) segments. Poly(tetramethyleneoxide) (PTMO) is amorphous and has a low T_g. The segment length was varied from 650 to 2800 g/mol by extending PTMO₆₅₀ using dimethyl isophthalate. The polymers were synthesized in the melt, and test samples were prepared by injection molding. The melting behavior, as well as the torsion modulus spectrum as a function of temperature, were studied using DSC and DMA, respectively. The T2T‐PTMO polymers were found to have sharp glass (T_g) and flow transitions (T_fl), and the modulus at the rubbery plateau appeared to be virtually temperature independent. The T_g value was found to be independent of the diamide concentration, thus indicating that the T2T segments were fully crystallized. The T_fl was found to decrease with increasing soft segment length; this was ascribed to a “solvent” effect of the amorphous phase of the crystalline T2T units. The difference between the melting and crystallization temperatures was found to be low, thus suggesting that on cooling, there is a high rate of crystallization. When ethanediol was added as a T2T segment extender, amide‐ester‐amide segments were introduced. These amide‐ester‐amide segments form a separate lamellar phase with a much higher melting temperature (>300°C). It was found that the crystallization rate of the T2T units was enhanced by the presence of the amide‐ester‐amide segments, indicating that upon cooling, the crystallized amide‐ester‐amide segments form the nucleation sites for the nonextended T2T segments. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1173–1180, 2001     

Processing of intractable polymers using reactive solvents. 6. A new reactive solvent concept based on reversible depolymerisation

The use of reactive solvents which reversibly (de)polymerise to facilitate the processing of poly(2,6-dimethyl-1,4-phenylene ether) (PPE) was explored. PPE can be dissolved at elevated temperatures in very low molecular weight thermoplastic poly(urethane) (TPU) fragments obtained via depolymerisation and these solutions can then be processed at the relatively low temperature of 250 °C. After processing and upon cooling, the TPU fragments repolymerise which induces a L-L phase separation between PPE and TPU followed by vitrification of the PPE matrix phase and at lower temperatures vitrification of the TPU dispersed phase. Since phase separation occurs during cooling, the phase separation is induced thermally as well as chemically, since the molecular weight of the ‘solvent’ increases upon lowering the temperature. The properties of the final materials, such as heat resistance, are dominated by the continuous PPE matrix. The starting molecular weight of TPU and the composition of the blend had pronounced effects on the phase separation, morphology and viscosity of the blends. Increasing the amount of TPU resulted in larger TPU particles but no effect on the T_g of the PPE-rich matrix was observed. Increasing the starting molecular weight of TPU resulted in higher phase separation temperatures and higher T_gs for the PPE-rich matrix. Possibilities for diminishing the residual TPU fractions were explored. The interference of vitrification with phase separation could be postponed and, consequently, the residual fraction of TPU in the PPE phase could be reduced either via an increase in the starting molecular weight of TPU or a decrease in cooling rate or T_g of the matrix.     

Structure and morphology of segmented polyurethanes: 1. Influence of incompatability on hard-segment sequence length

Separation of three polybutadiene/toluene diisocyanate/butane diol segmented polyurethanes by means of solvent extraction and the characterization of their fractions indicate that the molecules of the original polyurethanes are quite dissimilar in chemical composition and average hard-segment length. These polyurethanes are just blends of two fractions of segmented copolymer with very different average hard-segment content and average hard-segment length. For these polyurethanes, in addition to the segregation of the hard and soft segments, as expected usually for segmented copolymers, the segregation of macromolecules as a whole according to their composition should be considered in the interpretation of their morphology and properties and has been proved to be the origin of the existence of two hard-segment T_g's. This ind of compositional non-uniformity is the result of the poor compatibility between the components of the system. It should be a common phenomenon for segmented copolymers, but is especially obvious in the case of polybutadiene-containing polyurethanes owing to the extremely poor compatibility between their components.     

Crystallization of poly(ethylene terephthalate) modified with codiols

The nucleation of poly(ethylene terephthalate) (PET) by codiols and olefinic segments was studied. The codiols 1,5‐pentanediol, 1,8‐octanediol, 2,5‐hexanediol, and 1,3‐dihydroxymethyl benzene were copolymerized into PET in a concentration range of 0–10 mol %. The melting (T_m), crystallization (T_c), and glass‐transition (T_g) temperatures were studied. These codiols were found to be able to nucleate PET at low concentrations, probably by lowering the surface free energy of the chain fold. However, the codiols also disturbed the structural order of the polymer, resulting in a decrease in both the T_m and T_c values. The optimum codiol concentration was found to be at around 1 mol %, which is lower than previously reported. A diamide segment N,N′‐bis(p‐carbo‐methoxybenzoyl)ethanediamine (T2T) was found to be a more effective nucleator than the codiols; however, no synergy was observed between the nucleating effect of the diamide segment T2T and that of the codiol. An olefinic diol (C₃₆‐diol) with a molecular weight of 540 g/mol was also copolymerized into PET in a concentration range of 0–21 wt %. Only one T_g was observed in the resulting copolymers, suggesting that the amorphous phases of PET and the C₃₆‐diol are miscible. The main effect of incorporating the C₃₆‐diol into PET was the lowering of the T_g; thus, the C₃₆‐diol is an internal plastifier for PET. The C₃₆‐diol had little effect on the T_m value; however, the T_c value actually increased in the 11.5 wt % copolymer. As the T_g decreased and the T_c increased, the crystallization window also increased and thereby the likelihood of crystallization. Therefore, the thermally stable C₃₆‐diol appears to be an interesting compound that may be useful in improving the crystallization of PET. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2676–2682, 2001     

Differences in enthalpy recovery of gradient and random copolymers of similar overall composition: styrene/4-methylstyrene copolymers made by nitroxide-mediated controlled radical polymerization

Styrene/4-methylstyrene (S/MS) random and gradient copolymers were synthesized by nitroxide-mediated controlled radical polymerization (NM-CRP) and compared to random copolymers made by conventional free radical polymerization (ConvFRP). The gradient copolymers have molecular weight (MW) values approaching 85,000 g/mol, making these some of the higher MW gradient copolymers reported to date. Due to the proximity of the glass transition temperatures (T_g) of polystyrene (PS) and poly(4-methylstyrene) (PMS), there is no significant difference in T_g between the gradient and random copolymers, with both copolymer types yielding single T_gs that typically increase slightly with increasing MS content. While enthalpy relaxation studies demonstrate similarity in random copolymers made by NM-CRP and ConvFRP, they reveal significant differences between random and gradient copolymers. Gradient copolymers exhibit broad enthalpy recovery peaks, whereas random copolymers exhibit narrower enthalpy recovery peaks. The maxima in the enthalpy recovery peaks are at substantially lower temperature, as much as 17 °C, in the gradient copolymers as compared to random copolymers of equal overall composition. While random and gradient copolymers of a given overall composition exhibit similar enthalpy recovery values at a common physical aging time and quench depth relative to T_g, the major differences in the enthalpy recovery peaks indicate that differences in sequence distribution along the chain length can lead to unusual behavior in gradient copolymers relative to random copolymers.     

Influence of morphology on the properties of segmented block copolymers

A comparison was carried out regarding the structure and properties of segmented block copolymers with either non-crystallisable or crystallisable rigid segments. The flexible segment in the block copolymers was a linear poly(propylene oxide) end capped with poly(ethylene oxide), with a segment molecular weight of 2300 g/mol. The rigid segments were either non-crystallisable or monodisperse crystallisable polyamides of varying lengths. The morphologies were studied by TEM and AFM, the thermal mechanical properties by DMA and the elastic properties by compression set and tensile measurements. A direct comparison was made of segmented block copolymers with either liquid-liquid demixed or crystallised structures. The crystallised amide segments were more efficient in increasing the modulus and improving the elastic properties than the non-crystallisable ones. The copolymers with crystallised structures were transparent, had a low glass transition temperature of the polyether phase and a modulus that was independent of temperature between T_g and T_m. These copolymers also displayed a very low loss factor (tan δ), suggesting excellent dynamic properties. The hard phase in segmented block copolymers should thus preferably be crystalline.     

Microphase separation in copolymers of hydrophilic PEG blocks and hydrophobic tyrosine-derived segments using simultaneous SAXS/WAXS/DSC

Hydration- and temperature-induced microphase separations were investigated by simultaneous small- and wide-angle X-ray scattering (SAXS and WAXS) and differential scanning calorimetry (DSC) in a family of copolymers in which hydrophilic poly(ethylene glycol) (PEG) blocks are inserted randomly into a hydrophobic polymer made of either desaminotyrosyl-tyrosine ethyl ester (DTE) or iodinated I₂DTE segments. Iodination of the tyrosine rings in I₂DTE increased the X-ray contrast between the hydrophobic and hydrophilic segments in addition to facilitating the study of the effect of iodination on microphase separation. The formation of phase-separated, hydrated PEG domains is of considerable significance as it profoundly affects the polymer properties. The copolymers of DTE (or I₂DTE) and PEG are a useful model system, and the findings presented here may be applicable to other PEG-containing random copolymers. In copolymers of PEG and DTE and I₂DTE, the presence of PEG depressed the glass transition temperature (T_g) of the copolymer relative to the homopolymer, poly(DTE carbonate), and the DTE/I₂DTE segments hindered the crystallization of the PEG segments. In the dry state, at large PEG fractions (>70 vol%), the PEG domains self-assembled into an ordered structure with 14-18 nm distance between the domains. These domains gave rise to a SAXS peak at all temperatures in the iodinated polymers, but only above the T_g in non-iodinated polymers, due to the unexpected contrast-match between the crystalline PEG domains and the glassy DTE segments. Irrespective of whether PEG was crystalline or not, immersion of these copolymers in water resulted in the formation of hydrated PEG domains that were 10-20 nm apart. Since both water and the polymer chains must be mobile for the phase separation to occur, the PEG domains disappeared when the water froze, and reappeared as the ice began to melt. This transformation was reversible, and showed hysteresis as did the melting of ice and freezing of the water incorporated into the polymer. PEG-water complexes and PEG-water eutectics were observed in WAXS and DSC scans, respectively.     

Structure-property relations of poly(propylene oxide) block copolymers with monodisperse and polydisperse crystallisable segments

Segmented block copolymers with poly(propylene oxide) and crystallisable segments were synthesized and their structure-property relations studied. As crystallisable segments, amide units based on poly(p-xylylene terephthalamide), were used. The length of the amide segment was varied and these segments either had a monodisperse or random length distribution (polydisperse). The poly(propylene oxide) used was end capped with 20 wt% ethylene oxide (EO-tipped) and had a molecular weight of 2300 g/mol (M_n, incl. EO-tips). These segmented block copolymers are model block copolymers to gain insight in the structure-properties behaviour of related semi-crystalline segmented block copolymers, like polyether(urethane-urea)s. The morphology of the polyether(ester-amide)s (PEEA) was studied with TEM, the thermal properties with DSC and DMTA and the crystalline structures with WAXD. The elastic behaviour of the block copolymers was investigated in tensile and compression.Phase separation in PEEA's with crystallisable, short and monodisperse amide segments occurred by crystallisation, while with crystallisable random amide segments phase separation occurred through liquid-liquid demixing in combination with crystallisation. With short monodisperse amide segments, morphology of dispersed ribbons with a high aspect ratio was observed. PEEA's containing these monodisperse amide segments had higher moduli and better elastic properties as compared to PEEA's with random length amide segments. Increasing the length of the monodisperse amide segment increased the modulus and decreased the compression set of the corresponding blockcopolymers.     

Improved processability of PA66-polyimide copolymers with different polyimide contents

Limitations in the properties of polyamide PA66, such as low glass transition temperature and high water absorptivity, limit its applications. Introduction of amorphous polyimide segments into the PA66 main chain lowers the glass transition temperature and melting temperature and also improves its processability. PA66-polyimide (PA-PI) copolymers with different weight ratios of PI are prepared by high temperature and high-pressure solution polymerization. The degree of crystallization of PA-PI copolymers decreases with increasing PI content. The melting point decreases from 261°C for PA66 to 223°C for PA-PI-4. Dynamic mechanical analysis shows that the T_g increases from 70 to 90°C, and the storage modulus can be well maintained. Rheological studies show that the temperature for processing can reach 70°C. Copolymers with different PI contents show different processing viscosities. In addition, water absorptivity (about 1.8%) and dielectric constant values of PA-PI and PA6/6T are similar.     

Properties and crystallization kinetics of poly(ether ether ketone)‐co‐poly(ether ether ketone ketone) block copolymers

A series of block copolymers composed of poly(ether ether ketone) (PEEK) and poly(ether ether ketone ketone) (PEEKK) components were prepared from their corresponding oligomers via a nucleophlilic aromatic substitution reaction. Various properties of the copolymers were investigated with differential scanning calorimetry (DSC) and a tensile testing machine. The results show that the copolymers exhibited no phase separation and that the relationship between the glass‐transition temperature (T_g) and the compositions of the copolymers approximately followed the formula T_g = T_g1X₁ + T_g2X₂, where T_g1 and T_g2 are the glass‐transition‐temperature values of PEEK and PEEKK, respectively, and X₁ and X₂ are the corresponding molar fractions of the PEEK and PEEKK segments in the copolymers, respectively. These copolymers showed good tensile properties. The crystallization kinetics of the copolymers were studied. The Avrami equation was used to describe the isothermal crystallization process. The nonisothermal crystallization was described by modified Avrami analysis by Jeziorny and by a combination of the Avrami and Ozawa equations. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1652–1658, 2005     

Segmented blockcopolymers with uniform amide segments

Segmented blockcopolymers based on poly(tetramethylene oxide) (PTMO) soft segments and uniform crystallisable tetra-amide segments (TxTxT) are made via polycondensation. The PTMO soft segments, with a molecular weight of 1000 g/mol, are extended with terephthalic groups to a molecular weight of 6000 g/mol. The crystallisable segment is uniform of length and is based on a tetra-amide with terephthalamide groups. The length of the aliphatic diamine (x) in the tetra-amide segment is varied from x=2 to 8. The thermal properties of the blockcopolymers were studied with dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). Due to the use of uniform TxTxT segments a fast and almost complete crystallization of the hard segments is obtained. The melting temperature of the blockpolymers increases with decreasing diamine length and the well-known odd-even effect is observed. The elastic behavior of the blockcopolymer was studied by compression set. All the blockcopolymers had a low compression set and were highly elastic.     

Multiblock copolymers based on segments of poly (D,L‐lactic‐glycolic acid) and poly(ethylene glycol) or poly(ϵ‐caprolactone): A comparison of their thermal properties and degradation behavior

A comparison of the thermal properties of two classes of poly(D,L ‐lactic‐glycolic acid) multiblock copolymers is reported. In particular, the results of differential scanning calorimetry, and thermogravimetric analysis of copolymers containing poly(ethylene glycol) (PEG) or diol‐terminated poly(ϵ‐caprolactone) (PCDT) segments are described. The influence of the chemical structure and the length of PEG and PCDT on thermal stability, degree of crystallinity and glass transition temperature (T_g ) is discussed. Finally, an evaluation of the hydrolytic behavior in conditions mimicking the physiological environment is reported. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1721–1728, 2000