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     

Synthesis and characterization of block copolyetheresters with poly(tetramethylene 2,6-naphthalenedicarboxylate) segments

The block copolyetheresters with hard segments of poly(tetramethylene 2,6-naphthalenedicarboxylate) and soft segments of poly(tetramethylene oxide) were prepared by melt polycondensation of dimethyl 2,6-naphthalenedicarboxylate, 1,4-butanediol, and poly(tetramethylene ether) glycol (PTMEG) with molecular weights of 650, 1000, and 2000. The block copolymers were characterized by Fourier transform infrared and ¹H-NMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis (TGA), and X-ray diffraction. The block copolymer compositions were governed by the charge molar ratio (x) of PTMEG to dimethyl 2,6-naphthalenedicarboxylate. It was found that the thermal transitions were dependent on the compositions. As x increases, T_m and ΔH_m of the polyester segments decrease due to the decrease in the sequence length. The X-ray diffraction data also indicate that the crystallinity of the polyester segments decreased as x increased. The molecular weight of the PTMEG used has a significant influence on the glass transition temperature (T_g) and the crystallizability of the polyether segments. The polyether segments of block copolymers derived from PTMEG 2000 could crystallize after cooling and showed a T_g of about −67°C, independent of x. However, the polyether segments of copolymers derived from PTMEG 1000 and PTMEG 650 could not crystallize, and the T_g of the polyether segments decreased as x increased. This is described as the difference in the miscibility between amorphous parts of the polyether segments and those of the polyester segments. The TGA results indicate that the composition had little effect on the nonisothermal thermal degradation under nitrogen. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1411–1418, 1997     

ESR studies of polymer transitions. IV. Spin-probe studies of styrene block copolymers

ESR spin-probe values of glass temperatures are reported for a series of di-, tri-, and radial block copolymers. With one exception, in which the hard phase is poly(t-butylstyrene), the hard component is polystyrene (PS); the soft components include polybutadiene (PBD), polyisoprene (PI), hydrogenated PBD, hydrogenated PI, and poly(dimethyl siloxane) (PDMS). T_g's of the soft phase are in general agreement with those of the respective high molecular weight homopolymers; T_g's of the hard phase generally deviate widely from those of corresponding high molecular weight homopolymers. This deviation is interpreted in teens of a number of factors, including, the molecular weight of the hard phase, differences in solubility parameters for the two phases, percent of the hard phase present, and the presence of crystallinity. Comparison of T_g's determined by ESR with T_g's from dynamic mechanical methods on S-B-S triblocks of similar composition demonstrates that the ESR method is measuring the T_g of the interpliase and hence, in principle, its composition.     

Phase behavior for blends of styrene containing triblock copolymers with poly(2,6-dimethyl-1,4-phenylene oxide)

The extent to which the styrene end-blocks of three commercially available triblock copolymers can mix with a particular poly(2,6-dimethyl-1,4-phenylene oxide) (M_n = 22,600 and M_w = 34,000) or PPO has been examined by investigation of the glass transition behavior of the PPO and polystyrene (PS) portions of the blends using differential scanning calorimetry. Each block copolymer has a butadiene-based mid-block which was hydrogenated for two of these materials, but not the third. The three copolymers differ substantially in overall molecular weight and in molecula weight of the blocks. However, in analogy with the literature on blends of homopolymer polystyrene with styrene-based block copolymers, the molecular weight of the PS block should be the principal factor affecting the phase behavior in the present blends. Mixtures of the PPO with the block copolymers having PS blocks with M = 14,500 (nonhydrogenated midblock) and with M = 29,000 (hydrogenated mid-block) exhibited single composition-dependent T_gs for the hard phase, indicating complete mixing of PS segments with the PPO, for all proportions. On the other hand, the block copolymer having a PS block with M = 7,500 and a hydrogenated mid-block exhibited two separate hard phase T_gs corresponding to an essentially pure PPO phase and a PS-rich phase. For blends of homopolymer PS with styrene-based block copolymers, the similar two-phase behavior of the glassy portion can be readily explained by entropic considerations. For the present case, the favorable enthalpic contribution for mixing PPO and PS is an additional factor which seems to influence the restrictions on molecular weight for complete mixing; however, additional work is needed to develop a more quantitative assessment of this new issue.     

Novel poly(methyl methacrylate)‐block‐polyurethane‐block‐poly(methyl methacrylate) tri‐block copolymers through atom transfer radical polymerization

Poly(methyl methacrylate)‐block‐polyurethane‐block‐poly(methyl methacrylate) tri‐block copolymers have been synthesized successfully through atom transfer radical polymerization of methyl methacrylate using telechelic bromo‐terminated polyurethane/CuBr/N,N,N,N″,N″‐pentamethyldiethylenetriamine initiating system. As the time increases, the number‐average molecular weight increases linearly from 6400 to 37,000. This shows that the poly methyl methacrylate blocks were attached to polyurethane block. As the polymerization time increases, both conversion and molecular weight increased and the molecular weight increases linearly with increasing conversion. These results indicate that the formation of the tri‐block copolymers was through atom transfer radical polymerization mechanism. Proton nuclear magnetic resonance spectral results of the triblock copolymers show that the molar ratio between polyurethane and poly (methyl methacrylate) blocks is in the range of 1 : 16.3 to 1 : 449.4. Differential scanning calorimetry results show T_g of the soft segment at ?35°C and T_g of the hard segment at 75°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

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.     

Copolymers of poly(2,6-dimethyl-1,4-phenylene ether) and ester units

Copolymers of telechelic poly(2,6-dimethyl-1,4-phenylene ether) segments with terephthalic methyl ester endgroups (PPE-2T, 3700 g/mol) and different diols were made via a polycondensation reaction. The terephthalic endgroups of PPE-2T are stable during this reaction. The T_g of these polyether-ester copolymers decreases with increasing diol length and diol flexibility. The T_g can be set between 100 and 200 °C by changing the type of diol. However at increasing diol length the T_g becomes broader and the test bars are less transparent because the extent of phase separation increases with increasing diol length. Only polymers with a diol length up to C12 are homogeneous. Phase separation is probably enhanced by the bimodal molecular weight distribution of PPE-2T. Phase separation can be suppressed by using shorter PPE-2T segments with a short diol. It is even better to use fractionated, monomodal PPE-2T. Copolymerisation is much more effective in decreasing the T_g of PPE and therefore its processability than blending with polystyrene. It is expected that the processability of these copolymers is much better than that of PPE.     

Polymer composite of rigid and flexible molecules: Blend systems of poly(p-phenylene terephthalamide) and ABS resin

Homogeneous coagulant of poly(p-phenylene terephthalamide) (PPTA) and ABS resin was obtained by pouring the dimethylsulfoxide solution of N-sodium PPTA and ABS into acidic water. Transmission electron microscopic observation proved that PPTA was dispersed in the matrix in a form of microfibril with a diameter of 10–30 nm. The T_g of the resin component in ABS shifted to higher temperatures with increasing fraction of PPTA. Stress-strain behavior of the polymer composite showed increased tensile modulus and strength with addition of PPTA. The transition temperature from brittle to ductile fracture, however, shifted to higher temperature resulting in lower extensibility. Incorporation of the block copolymer of PPTA and polybutadiene into ABS improved the ultimate extensibility, i.e., increased toughness was provided compared with the simple composite systems of ABS and PPTA microfibrils. Scanning electron microscopic observation showed that the polymer composite made with the block copolymer generated many crazes upon deformation, while the composite with PPTA homopolymer fractured without remarkable craze formation. Thus, a new type of thermoplastic with improved mechanical properties was obtained by use of PPTA block copolymer as compatibilizer.     

Preparation and dynamic mechanical properties of poly(styrene‐b‐butadiene)‐modified clay nanocomposites

Polybutyl acrylate (PBA) was intercalated into clay by the method of multistep exchange reactions and diffusion polymerization. The clay interlayer surface is modified, and obtaining the modified clay. The structures of the clay‐PBA, clay‐GA (glutamic acid), and the clay‐DMSO (dimethyl sulfoxide) were characterized using X‐ray diffraction (XRD). The new hybrid nanocomposite thermoplastic elastomers were prepared by the clay‐PBA with poly(styrene‐b‐butadiene) block copolymer (SBS) through direct melt intercalation. The dynamic mechanical analysis (DMA) curves of the SBS/modified clay nanocomposites show that partial polystyrene segments of the SBS have intercalated into the modified clay interlayer and exhibited a new glass transition at about 157°C (T_g3). The glass transition temperature of polybutadiene segments (T_g1) and polystyrene segments out of the modified clay interlayer (T_g2) are about ?76 and 94°C, respectively, comparied with about ?79 and 100°C of the neat SBS, and they are basically unchanged. The T_g2 intensity of the SBS‐modified clay decreases with increasing the amounts of the modified clay, and the T_g3 intensity of the SBS‐modified clay decreases with increasing the amounts of the modified clay up to about 8.0 wt %. When the contents of the modified clay are less than about 8.0 wt %, the SBS‐modified clay nanocomposites are homogeneous and transparent. The T_gb and T_gs of the SBS‐clay (mass ratio = 98.0/2.0) are ?78.39 and 98.29°C, respectively. This result shows that the unmodified clay does not essentially affect the T_gb and T_gs of the SBS, and no interactions occur between the SBS and the unmodified clay. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1499–1503, 2002; DOI 10.1002/app.10353     

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.     

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): 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.     

Grafting of poly(3‐hydroxyalkanoate) and linoleic acid onto chitosan

Poly(3‐hydroxy octanoate) (PHO), poly(3‐hydroxy butyrate‐co‐3‐hydroxyvalerate) (PHBV), and linoleic acid were grafted onto chitosan via condensation reactions between carboxylic acids and amine groups. Unreacted PHAs and linoleic acid were eliminated via chloroform extraction and for elimination of unreacted chitosan were used 2 wt % of HOAc solution. The pure chitosan graft copolymers were isolated and then characterized by FTIR, ¹³C‐NMR (in solid state), DSC, and TGA. Microbial polyester percentage grafted onto chitosan backbone was varying from 7 to 52 wt % as a function of molecular weight of PHAs, namely as a function of steric effect. Solubility tests were also performed. Graft copolymers were soluble, partially soluble or insoluble in 2 wt % of HOAc depending on the amount of free primary amine groups on chitosan backbone or degree of grafting percent. Thermal analysis of PHO‐g‐Chitosan graft copolymers indicated that the plastizer effect of PHO by means that they showed melting transitions T_ms at 80, 100, and 113°C or a broad T_ms between 60.5–124.5°C and 75–125°C while pure chitosan showed a sharp T_m at 123°C. In comparison of the solubility and thermal properties of graft copolymers, linoleic acid derivatives of chitosan were used. Thus, the grafting of poly(3‐hydroxyalkanoate) and linoleic acid onto chitosan decrease the thermal stability of chitosan backbone. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:81–89, 2007     

Synthesis and properties of poly(imide siloxane) block copolymers with different block lengths

Several poly(imide siloxane) block copolymers with the same bis(γ‐aminopropyl)polydimethylsiloxane (APPS) content were prepared. The polyimide hard block was composed of 4,4′‐oxydianiline and 3,3′,4,4′‐diphenylthioether dianhydride (TDPA), and the polysiloxane soft block was composed of APPS and TDPA. The length of polysiloxane soft block increased simultaneously with increasing the length of polyimide hard block. For better understanding the structure–property relations, the corresponding randomly segmented poly(imide siloxane) copolymer was also prepared. These copolymers were characterized by FT‐IR, ¹H‐NMR, dynamic mechanical thermal analysis, thermogravimetric analysis, polarized optical microscope, rheology and tensile test. Two glass transition temperatures (T_g) were found in the randomly segmented copolymer, while three T_gs were found in the block copolymers. In addition, the T_gs, storage modulus, tensile modulus, solubility, elastic recovery, surface morphology and complex viscosity of the copolymers varied regularly with increasing the lengths of both blocks. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation of poly(styrene‐co‐isobornyl methacrylate) beads having controlled glass transition temperature by suspension polymerization

The styrene (St) and isobornyl methacrylate (IBMA) random copolymer beads with controlled glass transition temperature (T_g), in the range of 105–158°C, were successfully prepared by suspension polymerization. The influence of the ratios of IBMA in monomer feeds on the copolymerization yields, the molecular weights and molecular weight distributions of the produced copolymers, the copolymer compositions and the T_gs of these copolymers was investigated systematically. The monomer reactivity ratios were r₁ (St) = 0.57 and r₂ (IBMA) = 0.20 with benzyl peroxide as initiator at 90°C, respectively. As the mass fraction of IBMA in monomer feeds was about 40 wt %, it was observed that the monomer conversion could be up to 90 wt %. The fractions of IBMA unit in copolymers were in the range of 35–40 wt % and T_gs of the corresponding copolymers were in the range of 119.6–128°C while the monomer conversion increased from 0 to greater than 90 wt %. In addition, the effects of other factors, such as the dispersants, polymerization time and the initiator concentration on the copolymerization were also discussed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

High molecular weight diblock and ABA/ABC triblock copolymers of tert‐butyl (meth)acrylate

AB diblock copolymers were prepared by use of poly(tert‐butyl (meth)acrylate) (PtBA/PtBMA) as monofunctional macroinitiator in atom transfer radical polymerization of various (meth)acrylates (methyl, butyl) in the presence of the CuBr/N, N, N′, N′, N″‐pentamethyldiethylenetriamine catalyst system. Then using the diblock copolymer as macroinitiator with a bromine atom at the chain end, ABC and ABA triblock copolymers containing at least one PtBA or PtBMA segment were synthesized via polymerization of the selected (meth)acrylic monomer. Gel permeation chromatography was applied to determine molecular weights and polydispersity indices. The latter, for block copolymers prepared without deactivator addition, were in the range 1.2‐1.6 with a high degree of polymerization (150‐500). The chemical compositions of the block copolymers were characterized with ¹H nuclear magnetic resonance. The kind of combined segments and their lengths influenced the glass transition temperature (T_g) determined by differential scanning calorimetry. Copyright © 2012 Society of Chemical Industry     

Thermal analysis of styrene–alkyl methacrylate polymers. I. Glass transition temperatures

The glass transition temperatures (T_g's) of several polystyrenes and styrene–alkyl methacrylate copolymers and terpolymers were measured using thermomechanical analysis (TMA) and differential scanning calorimetry (DSC). The polymers studied had number-average molecular weights from 3000 to 250,000 g/mole. The results indicate that the composition dependence of the T_g's for the copolymers and terpolymers can be satisfactorily described by a general Fox equation. In general, the measured T_g's of the copolymer and terpolymer samples depend more on the steric effects of the constituent pendent groups than on their molecular weights. The chain flexibility rather than the size of the pendent group is the determining factor in the glass transition properties of the styrene polymers.     

Synthesis and characterization of ABA‐type block copolymers of trimethylene carbonate and ϵ‐caprolactone

This paper describes the synthesis of a series of ABA‐type triblock copolymers of trimethylene carbonate and ?‐caprolactone with various molar ratios and analyses the thermal and mechanical properties of the resulting copolymers. The structures of the triblock copolymers were characterized by ¹H and ¹³C nuclear magnetic resonance spectroscopy, FT‐IR spectroscopy and gel permeation chromatography. Results obtained from the various characterization methods proves the successful synthesis of block copolymers of trimethylene carbonate and ?‐caprolactone. The thermal properties of the block copolymers were investigated by differential scanning calorimetry. The T_m and ΔH_m values of the copolymers decrease with increasing content of trimethylene carbonate units. Two T_gs were found in the copolymers. Furthermore, both of the T_g values increased with increasing content of trimethylene carbonate units. The mechanical properties of the resulting copolymers were studied by using a tensile tester. The results indicated that the mechanical properties of the block copolymers are related to the molar ratio of trimethylene carbonate and ?‐caprolactone in the copolymers, as well as the molecular weights of the resulting copolymers. The block copolymer with a molar composition of 50/50 possessed the highest tensile stress at maximum and modulus of elasticity. Block copolymers possessing different properties could be obtained by adjusting the copolymer compositions. Copyright © 2004 Society of Chemical Industry     

Microhardness of styrene/butadiene block copolymer systems: Influence of molecular architecture

The influence of molecular architecture on the mechanical properties of styrene/butadiene block copolymers was investigated by means of the microhardness technique. It was found that the microhardness of the styrene/butadiene block copolymers is dictated by the nature of microphase separated morphology. In contrast to polymer blends and random copolymers, in which the microhardness generally follows the additivity rule, the behavior of the investigated block copolymers was found to significantly deviate depending on their molecular architecture. The glass‐transition temperature of the polystyrene phase (T_g‐PS), which practically remained constant and that of the polybutadiene phase (T_g‐PB), which varied with the change in the block copolymer architecture, apparently do not influence the microhardness values of the block copolymers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1670–1677, 2003