Preparation and characterization of poly(2‐methyl‐1,5‐pentamethylene oxamide) (PM52) polymer

Poly(2‐methyl‐1,5‐pentaneoxamide) ( PM52) with relative viscosity up to 3.3 were synthesized using 2‐methyl‐1,5‐pentanediamine (M52) and dibutyl oxalate via spray/melt polycondensation. The obtained polyoxamide was characterized by FTIR, ¹H‐NMR, WAXD, DSC, and TGA. The T_m of PM52 was 200°C with a heat of fusion (ΔH_f) of 59.7 J·g−¹, crystallization temperature of 125°C, and a crystallization enthalpy (ΔH_c) of 42.6 J·g⁻¹. Isothermal crystallization studies revealed a 2‐dimensional crystallization phenomenon which didn't vary with change in crystallization temperature. TGA analysis revealed that the thermal stability of PM52 compared well with commercial PA6, and XRD studies revealed an α form of crystal structure and that the polymers possessed good crystallinity. Saturated water absorption of 4.6 wt% was recorded for the new polyoxamide synthesized as compared with 10.6 wt% for commercial PA6; such properties are good for applications in the food industry, plastics, and electronics industry where dimensional stability is a key requirement.     

Homo‐ and Copolymerization of Phenacyl Methacrylate via the Atom Transfer Radical Polymerization Method

The homo‐ and copolymers via atom transfer radical (co)polymerization (ATRP) of phenacyl methacrylate (PAMA) with methyl methacrylate (MMA) and t‐butyl methacrylate (t‐BMA) was performed in bulk at 90°C in the presence of ethyl 2‐bromoacetate, cuprous(I)bromide (CuBr), and 2,2′‐bipyridine. The polymerization of PAMA was carried out at 70, 80, and 100°C. Also, free‐radical polymerization of PAMA was carried out at 60°C. Characterization using FT‐IR and ¹³C‐NMR techniques confirmed the formation of a five‐membered lactone ring through ATRP. The in situ addition of methylmethacrylate to a macroinitiator of poly(phenacyl methacrylate) [Mn=2800, Mw/Mn=1.16] afforded an AB‐type block copolymer [Mn=13600, Mw/Mn=1.46]. When PAMA units increased in the living copolymer system, the Mn values and the polydispersities were decreased (1.1<Mw/Mn<1.79). The monomer reactivity ratios were computed using Kelen‐Tüdös (K‐T), Fineman‐Ross (F‐R) and Tidwell‐Mortimer (T‐M) methods and were found to be r₁= 1.17; r₂= 0.76; r₁=1.16; r₂=0.75 and r₁=1.18; r₂=0.76, respectively (r₁=is monomer reactivity ratio of PAMA). The initial decomposition temperatures of the resulting copolymers were measured by TGA. Blends of poly(PAMA) and poly(MMA) obtained via the ATRP method have been characterized by differential thermal and thermogravimetric analyses.     

Block copolymerization of methylmethacrylate via ATRP method using a macroinitiator produced by ring opening polymerization: Characterization,dielectric properties,and a kinetic investigation

Poly(2-(3-methyl-3-phenylcyclobutyloxirane-co-?-caprolactone) [P(PCBO-co-?-CL)] was synthesized by ring opening polymerization (ROP) of 2-(3-methyl-3-phenylcyclobutyloxirane and ?-caprolactone (?-CL) using benzyl alcohol as the initiator and Sn(Oc)₂ as the catalyst. To produce a macroinitiator from copolymer with hydroxyl end group was carried out reaction of acylation with choloroacetyl chloride. The molecular structures of copolymers were confirmed by FT-IR, ¹H-NMR spectroscopies and gel permeation chromatography (GPC). A kinetic series of methyl methacrylate (MMA) via ATRP method were studied in the presence of this macroinitiator and using CuBr/2,2′-bipyridine (bpy) as catalyst at 110°C. The kinetic study showed that the polymerization proceeded in a controlled way up to high conversions and the number-average molecular weight (M_n) increased depending on time. The thermal properties of copolymers were evaluated by TGA and DSC measurements. The temperature and frequency dependence of dielectric constant (?) and dielectric loss factor (?″) of P[(PCBO-co-?-CL)-b-PMMA] and that of doped with different concentration of EuCl₃ were investigated between the frequency of 100–2000 Hz and temperature range (300–430 K). Also, the ac conductivity has been measured to see the effect of frequency and temperature.     

Effects of the architecture and environment on polymeric molecular assemblies of novel amphiphilic diblock copolynorbornenes with narrow polydispersity via living ring‐opening metathesis polymerization

Diblock copolymers of 5‐(methylphthalimide)bicyclo[2.2.1]hept‐2‐ene (NBMPI) and 1,5‐cyclooctadiene were synthesized by living ring‐opening metathesis polymerization with a well‐defined catalyst {RuCl₂(CHPh)[P(C₆H₁₁)₃]₂}. Unhydrogenated diblock copolymers showed two glass transitions due to poly(NBMPI) and polybutadiene segments, such as two glass‐transition temperatures at ?86.5 and 115.3 °C for poly 1a and ?87.2 and 115.3 °C for poly 1b . However, only one melting temperature could be observed for hydrogenated copolymers, such as 119.8 °C for poly 2a and 121.7 °C for poly 2b . The unhydrogenated diblock copolymer with the longer poly(NBMPI) chain (poly 1a ; temperature at 10% mass loss = 400 °C) exhibited better thermal stability than the one with the shorter poly(NBMPI) chain (poly 1b ; temperature at 10% mass loss = 385 °C). Two kinds of hydrogenated diblock copolymers, poly 2a and poly 2b , exhibited relatively poor solubility but better thermal stability than unhydrogenated diblock copolymers because of the polyethylene segments. Poly[(hydrochloride quaternized 2‐norbornene‐5‐methyleneamine)‐b‐butadiene]‐1 (poly 3a ) was obtained after the hydrolysis and quaternization of poly 1a . Dynamic light scattering measurements indicated that the hydrodynamic diameters of the cationic copolymer (poly 3a ) in water (hydrodynamic diameter = 1580 nm without salt), methanol/water (4/96 v/v; hydrodynamic diameter = 1500 nm without salt), and tetrahydrofuran/water (4/96 v/v; hydrodynamic diameter = 1200 nm without salt) decreased with increasing salt (NaCl) concentration. The effect of temperature on the hydrodynamic diameter of hydrophobically modified poly 3a was also studied. The inflection point of the hydrodynamic diameter of poly 3a was observed at various polymer concentrations around 30 °C. The critical micelle concentration of hydrophobically modified poly 3a was observed at 0.018 g dL^?1. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2901–2911, 2006     

Nanoporous Crosslinked Copolymers Prepared by Thermal Degradation of Poly(Methacryl‐N,N′‐diisopropylurea‐co‐ethylene Glycol Dimethacrylate)

Abstract

Copolymers of methacryl‐N,N′‐diisopropylurea (MA‐DiPrU) with ethylene glycol dimethacrylate (EDMA) at monomer‐to‐monomer ratios in the feed: 0.3/0.7; 0.5/0.5; 0.7/0.3; 0.8/0.2 were prepared in butanone in the presence of 2% of dibenzoyl peroxide (Bz₂O₂) at 70°C for 48?hr. Copolymers regardless of the ratio of comonomers in the feed decompose thermally at 200–250°C under the separation of isopropylisocyanate (iPrNCO). Residues after the removal of iPrNCO are thermally stable nanoporous crosslinked copolymers of methacryl‐isopropylamide (MA‐iPrA) with EDMA which decompose by a one‐step mechanism between 280°C and 450°C. Nonporous model copolymers poly(MA‐iPrA‐co‐EDMA) of similar composition, prepared by copolymerization of MA‐iPrA with EDMA, also decomposed by a one‐step mechanism as shown by TGA measurements.     

Properties and Structures of Terephthalyl Chloride (TPC) Modified meta‐Aramid Copolymers

The properties and structures of terephthalyl chloride (TPC) modified poly(m‐phenylene isophthalamide) (PMIA) with TPC mole content in acylchloride from 5%–15% were studied in this paper. The composition and structure of the copolymer were determined by ¹H NMR. The content of TPC moiety in the molecular chain was calculated. Thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) were used to analysis the thermal properties of TPC modified PMIA copolymer. The results show that by introducing TPC units in the PMIA molecular chain, PMIA copolymers with better thermal properties were prepared. With the increase of TPC content, the TPC modified PMIA exhibit increasing thermal stability. The pyrolysis process of the copolymer was detected by FTIR spectra. When the copolymers were pyrolyzed to 500°C, an aryl nitrile band at 2230 cm^?1 appears in the FTIR spectrum. This means that at this temperature breakage of the amide bond occurred.     

Synthesis and characterization of isomeric polyesters based on sebacic acid and hexanediols

Isomeric homopolymers and random copolyesters based on sebacic acid and isomeric hexanediols were synthesized by condensation techniques and characterized by NMR, GPC, intrinsic viscosity, and DSC. Among the homopolymers, only the polyester derived from the linear 1,6-hexanediol was found to be crystalline. Typical melting points were 65–70°C, depending on molecular weight, and a T_g of ?62°C was measured on a high molecular weight sample. Other isomeric homopolymers derived from the branched diols 2-methyl-2-ethyl-1,3-propanediol and 2,5-hexanediol were amorphous tacky fluids with glass temperatures of ?69 and ?66°C, respectively. In the case of the random copolymers, NMR analysis was particularly useful in determining the copolymer composition or the diol isomer ratio. DSC data indicated that all the random copolymers containing the linear 1,6-diol were crystallizable and their melting points depended on copolymer composition. The heat of fusion per repeat unit of poly(hexamethylene sebacate) was found to be 32 cal/g from measurements of the molecular weight dependence of the melting point.     

Ultrasonic Modification of Polymers. II. Degradation of Polystyrene,Substituted Polystyrene,and Poly(n-vinyl Carbazole) in the Presence of Flexible Chain Polymers

Abstract

Ultrasonic (20 kHz, 70 W) solution degradations of polystyrene, substituted polystyrenes, and poly(n-vinyl carbazole) have been carried in toluene and tetrahydrofuran at 27 and -20°C in the presence of flexible chain polymers. Polystyrene formed block copolymers at 27°C with stiff-chain polymer PVCz; however, in the presence of flexible chain polymers, e.g., poly(vinyl methyl ketone) or poly(vinyl methyl ether), there were no block copolymers formed. Poly(n-vinyl carbazole) does not seem to form any block copolymers at 27°C with flexible chain polymers, e.g., poly(octadecyl methacrylate) and poly(ethyl methacrylate). Poly(p-chlorostyrene) and poly(p-methoxystyrene) also do not form block copolymers at 27°C with poly(octadecyl methacrylate) but do so with poly(hexadecyl methacrylate). It is quite possible that these may only be blends of two homopolymers. Poly(octa-decyl methacrylate) does yield a block copolymer when sonicated at -15°C with poly(p-isopropyl α-methylstyrene).     

Co‐poly(aryl ether sulfone)s containing phthalimidine moiety in the main chain

Several new co‐poly(arylene ether sulfone)s have been prepared by the reaction of 4,4′‐fluorodiphenyl sulfone (FDS) with different bisphenols namely 4,4′‐isopropylidenediphenol (BPA), 4,4′‐hexafluoroisopropylidenediphenol (6F‐BPA), and N‐phenyl‐3,3‐bis(4‐hydroxyphenyl)phthalimidine(PA). The homo‐poly(arylene ether sulfone)s are named as 1a, 2a, and 3a. The copolymers namely 2b, 2c, 2d and 3b, 3c, 3d have been prepared, respectively, on reaction of FDS with BPA or 6F‐BPA using different molar ratios of PA such as 25, 50, and 75. The poly(aryl ether sulfone)s 1a containing PA unit in the main chain showed a very high glass transition temperature of 280°C and an outstanding thermal stability up to 510°C for 5% weight loss under synthetic air. Depending on the mole% of PA, the glass transition temperatures of the copolymers can be varied. The polymers were soluble in a wide range of organic solvents. Transparent thin films of these polymers exhibited tensile strengths upto 84 MPa and Young's modulus up to 3.16 GPa. The films of these polymers showed low water absorption of 0.24%. Copyright © 2009 John Wiley & Sons, Ltd.     

Rheological properties and enhanced oil recovery performance of a novel sulfonate polyacrylamide

A novel hydrosoluble sulfonate copolymer (SPAM) containing sulfonic acid groups was synthesized under mild conditions with Acrylamide (AM), 2-(Dimethylamino) ethyl methacrylate (DMAEMA) and 2-methyl-2-[(1-oxo-2-propenyl)amino]-1-propane sulfonic acid (AMPS) as monomers by segmentation initiation with 2,2'-azobis[2-methylpropionamidine] dihydrochloride and redox initiation system, respectively. The structures of copolymers were characterized by infrared (IR) spectroscopy, ¹H NMR spectroscopy and thermogravimetric analysis. The rheological properties of the copolymer solution at different shear rate, temperature and salt concentration were investigated. The shear-tolerance, temperature-tolerance and salt-tolerance of the novel synthetic hydrosoluble sulfonate copolymer are improved remarkably compared with partially hydrolyzed polyacrylamide (HPAM). The synthetic copolymer solution possesses a higher viscosity retention rate (53.3%) than HPAM (35.3%) at the total salinity of 20000 mg/L when temperature changed from 30°C to 99°C. The enhanced oil recovery (EOR) of the synthetic copolymer was performed by core flood, and the EOR degree of the synthetic copolymer in the 20000 mg/L salt solution at 80°C was better than that of HPAM. Compared with HPAM flooding, the EOR with the synthetic copolymer flooding was increased by 6.8% at 80°C.     

Novel Copolymers of Difluoro Ring-substituted 2-Phenyl-1,1-dicyanoethylenes with 4-Fluorostyrene: Synthesis,Structure and Dielectric Study

Copolymerization of fluorine ring-substituted 2-phenyl-1,1-dicyanoethenes, RC₆H₃CH?C(CN)₂ (R is 2,3-F,F, 2,4-F,F, 2,5-F,F, 2,6-F,F, and 4-CF₃) with 4-fluorostyrene were prepared in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the copolymers were characterized by IR, ¹H and ¹³C-NMR, GPC, DSC, and TGA. The monomer reactivity ratios for 4-fluorostyrene (M₁), r₁ = 0.6 and 2-(2,4-difluorophenyl)-1,1-dicyanoethene (M₂), r₂ = 0 were determined from Fineman-Ross plot. The order of relative reactivity (1/r₁) for difluoro-substituted monomers is 2,4-F,F (0.31) > 2,3-F,F (0.25) > 2,5-F,F (0.22) > 2,6-F,F (0.10). DSC curves showed that the copolymers were amorphous with high T _g in comparison with that poly(4-fluorostyrene) indicating a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer units. From the thermogravimetric analysis, the copolymers began to degrade in the range 214–260°C. The copolymer of 4-fluorostyrene and 2-(2,4-difluorophenyl)-1,1-dicyanoethene and poly(4-fluorostyrene) were dielectrically characterized in the range 25–200°C. The dominating relaxation process detected in both materials was the α-relaxation, associated with the dynamic glass transition. The relationship polarity-permittivity was discussed.     

Linear and Hyperbranched Poly(arylene ether)s from a New Semifluorinated AB Monomer

A new trifluoromethyl-activated AB monomer has been successfully synthesized by Pd-initiated coupling of 4-bromo anisole with 4-fluoro-3-trifluoromethylphenylboronic acid followed by demethylation. The monomer leads to a semifluorinated poly(arylene ether) by nucleophilic displacement polymerization reaction. The AB monomer has been further copolymerized with a corresponding AB ₂ monomer to form the corresponding semifluorinated hyperbranched (hb) poly(arylene ether). The resulting linear and hb poly(arylene ether)s exhibited weight average molecular weight of 75700 and 144100 g/mol, respectively. The hb copolymer exhibited better solubility in different organic solvents compared to the linear poly(arylene ether). The polymers showed excellent thermal stability up to 522°C at 10% wt loss in air and glass transition temperatures as high as 187°C. The mechanical properties of the linear poly(arylene ether) film 1a exhibited tensile strength at break of 89 MPa, elongation at break of up to 3% and a Young’s modulus value of 2.66 GPa. The films of the polymers were hydrophobic in nature and showed water contact angle as high as 93.6°.     

Synthesis,liquid crystalline mesophases and morphologies of diblock copolymers composed of a poly(dimethylsiloxane) block and a nematic liquid crystalline block

In this study, a series of liquid crystalline diblock copolymers, composed of a soft poly(dimethylsiloxane) (PDMS) block with a de?ned length and a side-on liquid crystalline poly(3??-acryloyloxypropyl 2,5-di(4?-butyloxybenzoyloxy) benzoate) (P3ADBB) block with different lengths, are synthesised by the atom transfer radical polymerisation. The macromolecular structures, liquid crystalline properties and the microphase-separated morphologies of the diblock copolymer are investigated by ¹H NMR, FT-IR, GPC, POM, DSC and TEM. The results show that the well-de?ned diblock copolymers (PDMS_n-b-P3ADBB_m) possess four different soft/rigid ratios (n = 58, m = 10, 25, 42, 66) and relatively narrow molecular distributions (PDI ≤ 1.30). P3ADBB blocks of the copolymers show nematic sub-phases, which are identical to the mesomorphic behaviour of the homopolymer P3ADBB. After being annealed at 90°C in a vacuum oven for 48 h, the copolymers form a lamellar morphology when m = 10 and morphologies of PDMS spheres embedded in P3ADBB matrix when m = 25, 42 and 66.     

Synthesis and Characterization of Four-Arm Star Poly(ϵ-caprolactone)-Block-Poly(cyclic-carbonate methacrylate) Copolymers by Combining Ring-Opening Polymerization With Atom Transfer Radical Polymerization

Well-defined four-arm star poly(?-caprolactone)-block-poly(cyclic carbonate methacrylate) (PCL-b-PCCMA) copolymers were synthesized by combining ring-opening polymerization (ROP) with atom transfer radical polymerization (ATRP). First, a four-arm poly(?-caprolactone) (PCL) macroinitiator [(PCL-Br)₄] was prepared by the ROP of ?-CL catalyzed by stannous octoate at 110°C in the presence of pentaerythritol as the tetrafunctional initiator followed by esterification with 2-bromoisobutyryl bromide. The sequential ATRP of CCMA monomer was carried out by using the (PCL-Br)₄ tetrafunctional macroinitiator (MI) and in the presence of CuBr/2, 2′-bipyridyl system in DMF at 80°C with [(MI)]:[CuBr]:[bipyridyl] = 1:1:3 to yield block polymers with controlled molecular weights (M_n (NMR) = 10700 to 27300 g/mol) by varying block lengths and with moderately narrow polydispersities (M_w/M_n = 1.2–1.4). Block copolymers with different PCL: PCCMA copolymer composition such as 50:50, 70:30 and 74:26 were prepared with good yields (48-74%). All these block copolymers were well characterized by NMR, FTIR and GPC and tested their thermal properties by DSC and TGA.     

Stimuli‐responsive ABC triblock copolymers by sequential living cationic copolymerization: Multistage self‐assemblies through micellization to open association

Stimuli‐responsive ABC triblock copolymers with three segments with different phase‐separation temperatures were synthesized via sequential living cationic copolymerization. The triblock copolymers exhibited sensitive thermally induced physical gelation (open association) through the formation of micelles. For example, an aqueous solution of EOVE₂₀₀‐b‐MOVE₂₀₀‐b‐EOEOVE₂₀₀ [where EOVE is 2‐ethoxyethyl vinyl ether, MOVE is 2‐methoxethyl vinyl ether and EOEOVE is 2‐(2‐ethoxy)ethoxyethyl vinyl ether; the order of the phase‐separation temperatures was poly(EOVE) (20 °C) < poly(EOEOVE) (41 °C) < poly(MOVE) (70 °C)] underwent multiple reversible transitions from sol (<20 °C) to micellization (20–41 °C) to physical gelation (physical crosslinking, 41–64 °C) and, finally, to precipitation (>64 °C). At 41–64 °C, the physical gel became stiffer than similar diblock or ABA triblock copolymers of the same molecular weight. Furthermore, the ABC triblock copolymers exhibited Weissenberg effects in semidilute aqueous solutions. In sharp contrast, another ABC triblock copolymer with a different arrangement, EOVE₂₀₀‐b‐EOEOVE₂₀₀‐b‐MOVE₂₀₀, scarcely exhibited any increase in viscosity above 41 °C. The temperatures of micelle formation and physical gelation corresponded to the phase‐separation temperatures of the segment types in the ABC triblock copolymer. No second‐stage association was observed for AB and ABA block copolymers with the same thermosensitive segments found in their ABC counterparts. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2601–2611, 2004     

Novel Copolymers of Styrene and Alkoxy Ring‐Substituted 2‐Phenyl‐1,1‐dicyanoethylenes

Electrophilic trisubstituted ethylene monomers, ring‐substituted 2‐phenyl‐1,1‐dicyanoethylenes, RC₆H₄CH?C(CN)₂ (where R is 2‐methoxy, 3‐methoxy, 4‐methoxy, 4‐ethoxy, 4‐propoxy, and 4‐butoxy), were synthesized by piperidine catalyzed Knoevenagel condensation of ring‐substituted benzaldehydes and malononitrile, and characterized by CHN elemental analysis, IR, ¹H‐ and ¹³C‐NMR. Novel copolymers of the ethylenes and styrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator (AIBN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H and ¹³C NMR, GPC, DSC, and TGA. High T _g of the copolymers in comparison with that of polystyrene indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. The gravimetric analysis indicated that the copolymers decompose in the 290–450°C range.     

Novel Copolymers of Styrene. 9. Methyl and Methoxy Ring-Substituted 2-Cyano-3-phenyl 2-propenamides

Novel electrophilic trisubstituted ethylene monomers, methyl and methoxy ring- substituted 2-cyano-3-phenyl-2-propenamides, RPhCH=C(CN)CONH₂, where R is 2,3-dimethyl, 2,4-dimethyl, 2,5-dimethyl, 2-(3-methoxyphenoxy), 2-(4-methoxyphenoxy), 3-(4-methoxyphenoxy), 4-(4-methylphenoxy), 2,3-methylenedioxy were prepared and copolymerized with styrene. The monomers were synthesized by potassium hydroxide catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and cyanoacetamide, and characterized by CHN elemental analysis, IR, ¹H- and ¹³C-NMR. Novel copolymers of the ethylenes and styrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator, ABCN at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H- and ¹³C-NMR, GPC, DSC, and TGA. High T_g of the copolymers in comparison with that of polystyrene indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500°C range with residue (5.8–33.8 wt%), which then decomposed in the 500–800°C range.     

Synthesis and Characterization of Novel Poly(Arylene Ether)s from 4,4′‐Thiodiphenol

Four novel perfluoroalkylated poly(arylene ether)s have been synthesized successfully using four perfluoroalkyl‐activated bisfluoro monomers. These polymers are synthesized through nucleophilic displacement of the fluorine atoms on the benzene ring with 4,4′‐thiodiphenol and are named as 1a, 1b, 1c and 1d, respectively. The polymers obtained by displacement of the fluorine atoms exhibit weight‐average molar masses up to 3.9×10⁴ g · mol^?1 in Gel permeation chromatography. These poly(arylene ether)s showed very high thermal stability up to 548°C for 10% weight loss in TGA under nitrogen and high glass transition temperature (T_g) up to 178°C in DSC depending on the repeat unit structures. The glass transition temperatures taken as peak in tan δ in DMA measurements are in good agreement with the DSC T_g values. All the polymers synthesized are soluble in a wide range of organic solvent such as CHCl₃, CHCl₂, THF, NMP, DMF and toluene. Transparent thin films of these polymers cast from THF exhibited tensile strengths up to 72 MPa, modulus up to 1.69 GPa with low elongation at break depending on their exact repeating unit structures. Rheological properties showed ease of processability of these polymers with no change in melt viscosity with temperature.     

Self-assembled and Nanostructured Copolymer Aggregations of the Tertiary Amine Methacrylate Based Triblock Copolymers

The micellization behavior of novel tertiary amine methacrylate-based ABA type triblock copolymers formed by poly[2-(dimethylamino)ethyl methacrylate] [PDMA] middle block and poly[2-(diethylamino)ethyl methacrylate] [PDEA] or poly[2-(diisopropylamino)ethyl methacrylate] [PDPA] side blocks, PDPA_m-b-PDMA_n-b-PDPA_l, and PDEA_m-b-PDMA_n-b-PDEA_l was investigated. Both types of triblock copolymers were water-soluble and had potential for various applications due to their self-assembled and the bottom-up nanoscale micellar construction. The micellar aggregations of the triblock copolymers in aqueous solutions with varying comonomer ratios, molecular weights, temperatures, and pH values were investigated by small-angle X-ray scattering and dynamic light scattering. Compact micellar aggregations were obtained as 0.5 weight percent solutions at 20–21°C and pH 8.67 to 9.05, and characterized as polydispersed spherical core-shells. One group of triblock copolymer micelles had PDPA-cores with radii from 18 to 21 Å and PDMA-shell thicknesses of 89–105 Å, whereas the other group had PDEA-core spherical micelles with core radii of 60–62 Å and a PDMA-shell thicknesses of 64–66 Å.     

Poly(N-isopropylacrylamide-co-N-t-butylacrylamide)-block-poly(ethylene glycol)-block-poly(N-isopropylacrylamide-co-N-t-butylacrylamide) triblock copolymers: synthesis and thermogelation properties of aqueous solutions

Novel triblock copolymers with PEG middle blocks of 1–10 kDa and poly(N-isopropylacrylamide-co-t-butylacrylamide) statistical copolymer side arms with DP_n?≈?88 and different compositions, were synthesized by SET-LRP. The thermogelation properties of their aqueous solutions depended on both hydrophobic monomer content of the side blocks and molecular weight (MW) of the poly(ethylene glycol) (PEG) middle block, as proven by dynamic rheometry, DSC, and tube inversion method measurements. At constant PEG chain length, increasing TBAM proportions led to a gelation process occurring at progressively lower temperatures, as well as to a lower stability of the forming hydrogels in the case of shorter-PEG-chain block copolymers. By employing longer PEG blocks (M_PEG ≥6,000 Da), stable hydrogels with the gelation temperature below 37 °C could be obtained. For a constant composition of the copolyacrylamide blocks, the dependence of the phase transition temperature (T_ph) on M_PEG displayed a different shape at different polymer solution concentrations, because of the stronger variation of T_ph with polymer concentration as M_PEG increased. Also, the viscoelastic properties of the hydrogels resulting from 20 wt.% polymer aqueous solutions at 37 °C were stronger affected by the MW of the PEG middle block than by the hydrophobic character of the thermosensitive side blocks.