Sequential reordering in condensation copolymers, 1. Melting- and crystallization-induced sequential reordering in immiscible blends of poly(ethylene terephthalate) with polycarbonate or polyarylate

Unlike previous attempts, the entire cycle of melting- and crystallization-induced reordering is realized in binary polymer blends in the following order: two homopolymers → block copolymer → random copolymer → block copolymer. Blends of poly(ethylene terephthalate)

1 Systematic IUPAC name: poly(oxyethyleneoxyterephthaloyl).

(PET) and bisphenol-A/polycarbonate (PC) as well as PET/polyarylate (PAr) blends, are annealed directly in a differential scanning calorimeter at 280°C for various times. Scanning the samples in the heating mode reveals the complete disappearance of crystallization or melting in the blends where the ratio of PET/PC repeating units is less than 5.7/1.0. Such an amorphization is attributed to the formation of random copolymers. This statement is confirmed by NMR measurements, by the observation of one glass transition temperature T_g in the range between the initial two T_gs, and by solubility tests. Once randomized, annealing the samples at 235°C and 245°C, i. e., below melting of PET, results in a T_g shift toward the T_g of PET as well as in reappearance of melting. This effect is accompanied by an eight-fold crystallinity increase in the equimolar blend, as compared to the randomized sample. The regenerated crystallization ability is explained by restoration of the blocks. According to previous findings, it is concluded that the considerable enthropy increase is the main driving force of randomization. The rival trend to the formation of a block copolymer by sequential reordering is driven by the crystallization of PET blocks formed. The conclusion that the observed changes in the crystallization ability and T_g-values are based on sequential reordering is supported by experiments with samples containing increased amounts of transesterification catalyst leading to a much faster appearance of these changes. No randomization is observed with the blend composition ratio of repeating units PET/PC > 5.7/1.0. When the annealing is performed for 300 min at 165°C, where no significant exchange reactions are expected to occur, no restoration of the crystallization ability is observed.     

Miscibility behavior in blends of poly(2,6-dimethylphenylene oxide) and random or block copolymers of styrene with methyl methacrylate

The Miscibility in blends of poly(2,6-dimethylphenylene oxide)

1 Systematic IUPAC name: poly[oxy(2,6-dimethyl-1,4-phenylene)].

(PPO) with random or block copolymers of styrene and methyl methacrylate (MMA) was studied by light microscopy and glass transition temperature measurements. Blends of PPO and the random copolymers were found to be miscible up to a copolymer content of 18 wt.-% MMA. The transition from miscibility to immiscibility in these blends in independent of temperature in the range 100 to 350°C. From these data, the segmental interaction parameter between units of the homopolymer and MMA, χ_PPO/PMMA is estimated to be about 0,5. Blends of PPO and the block copolymers of styrene and MMA used behave essentially as the corresponding homopolymers in terms of miscibility.     

Micelle formation and anomalous behaviour in the system polystyrene-block-poly(ethylene/propene)/poly(isobutene)/5-methyl-2-hexanone

Solubilization of poly(isobutene)

1 Systematic IUPAC name: poly(1,1-dimethylethylene).

by micelles of polystyrene-block-poly(ethylene/propene) block copolymer with a copoly(ethylene/propene) core was investigated. The weight of poly(isobutene) solubilized was found to be proportional to the concentration of block copolymer in the solution. No influence of the presence of poly(isobutene) on the critical micelle temperatures has been found. However, the addition of poly(isobutene) to the micellar solution seems to favour the anomalous behaviour found in micellar solutions of the block copolymers used in this study.     

Influence of chemical structure on glass transition temperatures of poly(propylene terephthalate) and poly(propylene isophthalate)

Poly(propylene terephthalate)

1 Systematic IUPAC name: poly(oxypropyleneoxyterephthaloyl).

(PPTP) and poly(propylene isophthalate)

2 Systematic IUPAC name: poly(oxypropyleneoxyisophthaloyl).

(PPIP) were prepared by melt polycondensation. Different fractions with number-average molar masses in the range 5 000 ? 20 000 g·mol^?1 were obtained and their respective glass transition temperatures (T_g) determined by calorimetry. The solubility parameters of the polymers were obtained by viscosity measurements in different solvents and were found to be 9,4 and 9,5 cal^1/2·cm^?3/2 (19,2·10³ and 19,4·10³ J^1/2·m^?3/2) for PPIP and PPTP, respectively. The glass transition temperatures were compared with those reported for analogous polyesters and it was shown that intramolecular interactions highly influence the T_g of these polyesters, whereas the effect of intermolecular interactions seems to be less important.     

Sequential reordering in condensation copolymers, 2. Melting- and crystallization-induced sequential reordering in miscible poly(butylene terephthalate)/polyarylate blends

A 50/50 (weight ratio (38/62 mole ratio referred to repeating units)) blend of poly(butylene terephthalate) (PBT) and polyarylate (PAr), was studied by means of thermal, solubility, X-ray and nuclear magnetic resonance techniques after annealing procedures that enable transesterification. Prolonged thermal treatment at 290°C gives rise to a copolymer that no longer reveals melting or crystallization. In accordance with previous reports, this effect is attributed to the formation of a random copolymer. Additional annealing of such samples at the relatively low temperature of 140°C results in the reappearance of melting endotherms in the differential scanning calorimetry curves. This effect is explained by crystallization-induced sequential reordering from random to block copolymer by means of transreactions. In that way a PBT/PAr blend was shown to be another polymer system, along with poly(ethylene terephthalate) (PET)/polycarbonate (PC) and PET/PAr blends, in which the entire cycle is realized, from two homopolymers via a block- and random copolymer to a block copolymer. The unusually low temperature at which the crystallization-induced sequential reordering to block polymers takes place is explained by the miscibility of PBT and PAr which enables transreactions to take place in the bulk.     

Morphology and properties of polybutadiene- and polyether-polyurethane zwitterionomers

Two series of polyurethane zwitterionomers based on 4,4′-methylene-di(phenyl isocyanate) (MDI), N-methyl diethanolamine (MDEA)

1 Systematic IUPAC name: 2,2′-(methylimino)diethanol.

, and either 1350 molecular weight hydroxyl terminated polybutadiene or 1000 molecular weight poly(tetramethylene oxide)

2 Systematic IUPAC name: poly(oxytetramethylene).

were synthesized. Zwitterionization was accomplished by quaternizing the tertiary amine of MDEA with 1,3-pro-panesultone. In Both series, IR analysis suggests that the sulfonate ion SO₃^? associates with the counter ion on the chain extender and the acidic hydrogen of the urethane linkage. Ammonium sulfonation shifts the soft segment T_g of polyether-based material to lower temperatures suggesting that ionization improves microphase separation. The soft segment T_g of the polybutadiene system is unaffected by ionization. IR dichroism measurements show that with increasing ammonium sulfonation both the hard and soft segments in the polyether-polyurethane zwitterionomers orient to a greater extent with deformation. In contrast, in the poly-butadiene-based zwitterionomers the orientability of the hard segment decreased with ionization while the soft segment showed significant chain alignment. Coupling the dichroism measurements to stress-strain results suggests that the hard segment domains of the polyether-polyurethane system possess more of an interconnected structure, while the polybutadiene-poly-urethane system contains hard segment domains which are largely isolated. The formation of different morphologies in the two systems of zwitterionomers may be due to the different interdomain surface tensions.     

Poly(ether/ester)s based on poly(butylene terephthalate) and poly(ethylene glycol), 1. Poly(ether/ester)s with various polyether: polyester ratios

A series of poly(ether/ester)s 1 based on poly(butylene terephthalate)

1 Systematic IUPAC nomenclature: poly(oxytetramethyleneoxyterephthaloyl).

and poly(ethylene glycol) is synthesized. ¹H and ¹³C nuclear magnetic resonance, infrared and differential scanning calorimetry (DSC) measurements prove a block structure of the prepared copolymers. The DSC curves suggest the existence of a three-phase morphology — two amorphous phases for both polyether and polyester segments, and a crystalline phase for the polyester segments. Small angle X-ray scattering (SAXS) measurements lead to the same conclusion. The degree of crystallinity assigned to the polyester fraction differs insignificantly and is similar to that of the homopolymer. SAXS data show approximately the same long spacing for all crystallizable copolymers. The tensile parameters of the studied polymers are similar to those of available commercial products based on poly(butylene terephthalate) and poly(tetrahydrofuran).     

(Co)polymers of L-lactide, 1. Synthesis,thermal properties and hydrolytic degradation

Copolymers of L -lactide with D -lactide

1 According to IUPAC the name dilactide is preferred to lactide.

, glycolide

2 IUPAC name: diglycolide.

, ε-caprolactone and trimethylene carbonate, and networks with spiro-bis-dimethylene-carbonate (2,4,7,9-tetraoxaspiro[5.5]undecane-3,8-dione) were prepared in bulk at standardized polymerization conditions. The properties of the nascent copolymers were evaluated with respect to the nature of the comonomer. Copolymerization with comonomers entailing low glass transition temperature simultaneously reduces the crystallinity. 300 MHz ¹H nuclear magnetic resonance is shown to be a useful technique for the determination of the average monomer sequence lengths in ε-caprolactone and trimethylene carbonate copolymers. The presence of crystallizable L -lactide sequences, due to differences in monomer reactivity, has a large effect on the thermal properties of the copolymer as well as on the long-term degradation characteristics.     

Investigation on the spherulitic morphology of poly(ether-ether-ketone)

The spherulitic morphology of poly(ether-ether-ketone)

1 Systematic name: poly(oxy-1, 4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene).

(PEEK) has been studied by using polarizing light microscopy, IR and differential scanning calorimetry. It has been found that in distinct cases the spherulites of PEEK show radiated or banded morphology, which can change from one to another upon thermal treatment. The process was found to be reversible and also affected by the film thickness.     

Poly[N-(2-hydroxyethyl)ethyleneimine-co-(1,2,3,6-tetrahydrophthalic anhydride)] by spontaneous copolymerization

The copolymerization of 1,2,3,6-tetrahydrophthalic anhydride (THPhA) as electrophilic monomer and N-(2-hydroxyethyl)ethyleneimine

1 Systematic name: N-(2-hydroxyethyl)aziridine.

as nucleophilic monomer in acetonitrile without initiator was investigated. The copolymers show low incorporation of THPhA in the main chain and preferential incorporation in the side chain by esterification reaction of the hydroxymethyl group. On the basis of the spectroscopic data a copolymer structure is proposed.     

Fourier transform infrared spectroscopic study of polyacetylene, 2. Thermal isomerization kinetics and mechanism

Thermal isomerization kinetics of high Z (>90%) rare-earth polyacetylene

1 IUPAC name: poly(vinylene).

was studied by Fourier transform infrared spectrophotometry in the temperature range of 354 to 443 K. The isomerization kinetics do not follow any simple kinetic reaction order; the apparent activation energy was determined to be 48,1 kJ·mol^?1. The Z to E isomerization in polyacetylene is discussed in terms of a diradical two-step mechanism.     

Novel synthesis of poly(benzoin) and poly(benzil). Characterization and application as photosensitizer materials

New photoactive polymers containing benzoin or benzil groups have been prepared by condensation of terephthalaldehyde. The influence of the alkali metal ions and solvents used upon the progress of polycondensation and yield of poly(benzoin)

1 Systematic name: Poly(1,4-phenylene-1-hydroxy-2-oxoethylene).

were studied. Oxidation of this polymer by nitric acid or ammonium nitrate in acetic acid afforded the corresponding poly(benzil)

2 Systematic name: Poly(1,4-phenylene-1,2-dioxoethylene).

in quantitative yield. The resulting polymers were confirmed by elemental analysis, IR, ¹H NMR and UV/visible spectral data, and characterized using viscometry, DTA measurements, thermogravimetric and X-ray analysis. The photosensitizing property of the prepared polymers was detected by fluorescence. It was found that irradiation of poly(benzoin) in DMSO solution at 285 nm causes yellow fluorescence whereas poly(benzil) does not display fluorescence at the same excitation wavelength. Moreover, the use of poly(benzil) as photosensitizer material in the photochemical cleavage of thiourea and its derivatives was also studied.     

Fourier transform infrared spectroscopic study of polyacetylene, 1. Spectral assignment and characteristics of Z/E (“cis”/“trans”) geometric isomers

An FTIR spectroscopic study was carried out for rare-earth polyacetylenes

1 IUPAC name: poly(vinylene).

(PA) containing both Z (“cis”) and E (“trans”)

2 We distinguish formally between configurations (Z, E = “cis”, “trans”) and conformations (cis, trans), though in the case of poly(vinylene) the physical quality is virtually the same.

geometric isomers. Spectral assignments were made by the study of PA samples with different Z/E ratios and by referring to the known assignment of the IR spectrum of PA obtained with Ti(OC₄H₉)₄·Al(C₂H₅)₃. The conjugation effect of Z or E ? CH?CH? sequences and their length distribution in PA are investigated by spectral subtraction and peak separation. It is shown that the frequency of v(CH) (out-of-plane deformation) is located in the regions 741 to 747 cm^?1 and 940 to 1014 cm^?1 for Z- and E-PA, respectively, depending on the conjugation length. At the beginning of thermal isomerization of Z-PA, long Z sequences are interrupted quite frequently; this causes a shift of v(CH) towards higher frequencies. In high E-PA obtained by thermal isomerization of Z-PA, uninterrupted long E sequences persist. This demonstrates that a crosslinking reaction between PA chains is not conspicuous during the thermal isomerization process.     

Synthesis and reaction of polymethacrylate bearing cyclic carbonate moieties in the side chain

(2-Oxo-1,3-dioxolan-4-yl)methyl methacrylate ( 6 ) was prepared by fixation of CO₂ into glycidyl

1 Systematic name: 2,3-epoxypropyl.

methacrylate (2) . Pure 6 polymerized spontaneously at room temperature. Radical polymerization of 6 (purity 94%) was carried out at 60°C using 2,2′-azoisobutyronitrile as an initiator in dimethyl sulfoxide (DMSO) to give the corresponding homopolymer 1 (yield: 99%) which is soluble in DMSO and N,N-dimethylformamide. 1 was reacted with butylamien at room temperature in DMSO for 24 h to the corresponding polymethacrylate 13 (yield: 100%) having a hydroxyurethane

2 The systematic name for urethanes is carbamates.

group in the side chain. No reaction of the ester groups of 1 with butylamine was observed. This was also demonstrated by the model reaction of (2-oxo-1,3-dioxolan-4-yl)methyl isobutyrate (9) with butylamine in which the corresponding hydroxyurethanes 10 , 11 and 12 were isolated in 96% yield.     

Solution properties and light scattering measurements of poly(2,5-pyrimidinediylterephthalamide)

A Series of chains of different molecular weight of the fully aromatic polyamide poly(2,5-pyrimidinediylterephthalamide)

1 IUPAC name: poly(2,5-pyrimidinediyliminoterephthaloylimino).

(PPYMT) in the solvents 96 wt.-% sulfuric acid and methanesulfonic acid have been characterized by means of static and dynamic light scattering, dilute solution viscosimetry and measurements of the critical polymer volume fraction for the onset of a nematic phase. The experimental results are in good agreement with a model of stiff worm-like chains for the solution conformation of PPYMT, and the persistence length is estimated to be ca. 150 Å (lower limit: 50–100 Å).     

One and two component hydrogels, 3. Deswelling and compression measurements on one component hydrogels

The value of the Flory-Huggins interaction parameter for water and poly(N-vinyl-2-pyrrolidone)

1 Systematic nomenclature: Poly[l-(2-oxo-l-pyrrolidinyl)ethylene].

(PVP), networks is determined by combining uni-directional compression measurements in the swollen state with network deswelling measurements. It was found that the dependance of the parameter on crosslink density can be explained by considering the interaction of water with the crosslinking molecule, a very water insoluble compound. Moreover, it was found that the interaction parameter within the swelling range studied is independant of network concentration. The number of elastically effective network chains is overestimated by a substantial margin.     

Study on the internal friction characteristics of a polyaryl ether sulfone with bulky substituent below the glass transition temperature

The temperature and frequency dependence of internal friction of a polyaryl ether sulfone with cardo side groups

1 Systematic name: poly(phthalidylidene-1,4-phenyleneoxy-1,4-phenylenesulfonyl-1,4-phenyleneoxy-1,4-phenylene).

( 1 ) are measured using a multi-function torsion pendulum below the glass transition temperature (531 K). Two relaxation peaks are observed at 328 K and 150 K (for 0,1 Hz). The elementary processes of the two relaxations are found to be different from each other: the relaxation at higher temperature is an ordering process and that at lower temperature is a disordering one.     

Copolymerization of 5-norbornen-2-yl acetate with cycloalkenes by the metathesis catalyst WCl6/(CH3)4Sn

Ring-opening metathesis copolymerization of 5-norbornen-2-yl

1 System. name: bicyclo[2.2.1]hept-5-en-2-yl.

acetate (NBEAc; 80% endo) with cyclooctene (COE) and norbornene

2 System. name: bicyclo[2.2.1]hept-2-ene.

(NBE) was studied using WCl₆/(CH₃)₄Sn as catalytic system. The copolymerization parameters (r₁ = r₂ = 1 for the NBEAc/NBE system and r₁ = 1/r₂ = 132 for the NBEAc/COE system) show that the reactivity of the monomers is not affected by the presence of an ester substituent but that it depends on the structure of the hydrocarbon cycle. Thus the well known inhibition effect of the ester group may be concluded not to lie in the propagation step of the catalytic cycle.     

Linear polymerization of endo-dicyclopentadiene initiated by metathesis catalysts

The polymerization of endo-dicyclopentadiene

1 Systematic name of endo-dicyclopentadiene is: tricyclo[5.2.1.0^2,6]deca-3,8-diene.

(endo-DCP) by the metathesis catalyst ReCl₅/(CH₃)₄ Sn gave a substantial yield of a linear polymer with high molecular weight and high content of cis double bonds. The kinetics of the early stage of the reaction was studied by calorimetry. The polymerization proceeds via an oligomerization reaction followed by the formation of polymers. A mechanistic scheme is proposed to explain the generation of the primary active species and the two-step polymerization process.