Synthesis and characterization of well‐defined random and block copolymers of ε‐caprolactone with l‐lactide as an additive for toughening polylactide: Influence of the molecular architecture

Well‐defined multiarmed star random and block copolymers of ε‐caprolactone with l ‐lactide with controlled molecular weights, low polydispersities, and precise numbers of arms were synthesized by the ring‐opening polymerization of respective cyclic ester monomers. The polymers were characterized by ¹H‐NMR and ¹³C‐NMR to determine their chemical composition, molecular structure, degree of randomness, and proof of block copolymer formation. Gel permeation chromatography was used to establish the degree of branching. Star‐branched random copolymers exhibited lower glass‐transition temperatures (T_g's) compared to a linear random copolymer. When the star random copolymers were melt‐blended with poly(l ‐lactic acid) (PLA), we observed that the elongation of the blend increased with the number of arms of the copolymer. Six‐armed block copolymers, which exhibited higher T_g's, caused the maximum improvement in elongation. In all cases, improvements in the elongation were achieved with no loss of stiffness in the PLA blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43267.     

Synthesis and characterization of ABA type tri‐block copolymers derived from p‐dioxanone,L‐lactide and poly(ethylene glycol)

A series of triblock co‐polymers, consisting of a poly(ethylene glycol) (PEG) central block joined to two blocks of random p‐dioxanone‐co‐L ‐lactide copolymers were synthesized by ring‐opening polymerization of p‐dioxanone (PDO) and L ‐lactide (LLA) initiated by PEG in the presence of stannous 2‐ethylhexanoate catalyst. The resulting copolymers were characterized by various techniques including ¹H and ¹³C NMR and FTIR spectroscopies, gel permeation chromatography, inherent viscosity, wide‐angle X‐ray diffractometry (WAXD) and differential scanning calorimetry (DSC). The conversion of PDO and L ‐lactide into the polymer was studied various mole ratios and at different polymerization temperature from ¹H NMR spectra. Results of WAXD and DSC showed that the crystallinity of PEG macroinitiator was greatly influenced by the composition of PDO and L ‐lactide in the copolymer. The triblock copolymers with low molecular weight were soluble in water at below room temperature. © 2003 Society of Chemical Industry     

Effect of acrylic acid neutralization on ‘livingness’ of poly[styrene‐ran‐(acrylic acid)] macro‐initiators for nitroxide‐mediated polymerization of styrene

BACKGROUND: The effect of acrylic acid neutralization on the degradation of alkoxyamine initiators for nitroxide‐mediated polymerization (NMP) was studied using styrene/acrylic acid and styrene/sodium acrylate random copolymers (20 mol% initial acrylate feed concentration) as macro‐initiators. The random copolymers were re‐initiated with fresh styrene in 1,4‐dioxane at 110 °C at SG1 mediator/BlocBuilder^® unimolecular initiator ratios of 5 and 10 mol%. RESULTS: The value of k_pK (k_p = propagation rate constant, K = equilibrium constant) was not significantly different for styrene/acrylic acid and styrene/sodium acrylate compositions at 110 °C (k_pK = 2.4 × 10^?6–4.6 × 10^?6 s^?1) and agreed closely with that for styrene homopolymerization at the same conditions (k_pK = 2.7 × 10^?6–3.0 × 10^?6 s^?1). All random copolymers had monomodal, narrow molecular weight distributions (polydispersity index M?_w/M?_n = 1.10–1.22) with similar number‐average molecular weights M?_n = 19.3–22.1 kg mol^?1. Re‐initiation of styrene/acrylic acid random copolymers with styrene resulted in block copolymers with broader molecular weight distributions (M?_w/M?_n = 1.37–2.04) compared to chains re‐initiated by styrene/sodium acrylate random copolymers (M?_w/M?_n = 1.33). CONCLUSIONS: Acrylic acid degradation of the alkoxyamines was prevented by neutralization of acrylic acid and allowed more SG1‐terminated chains to re‐initiate the polymerization of a second styrenic block by NMP. Copyright © 2008 Society of Chemical Industry     

Synthesis of two‐end‐functionalized copolymer of styrene and methyl methacrylate via living radical polymerization

The random copolymers (HO‐P(St‐r‐MMA)‐COOH) of styrene (St) and methyl methacrylate (MMA) with hydroxyl group at one end and carboxyl group at another end were synthesized by nitroxide‐mediated living radical polymerization initiated by 4,4′‐azobis(4‐cyanovaleric acid) (ACVA) and 4‐hydroxyl‐2,2,6,6–tetramethylpiperidineoxyl (TEMPO‐OH). The experimental results have shown that all synthesized copolymers have narrow molecular weight distribution. The conversion of monomers and the molecular weight of copolymer increase with polymerization time. Thus, a copolymerization mechanism containing living radical polymerization is suggested. The use of this method permits the copolymer with two functional chain ends and controllable molecular weight as well as low molecular weight distribution. X‐ray photoelectron spectroscopy result shows that the synthesized copolymers can be tethered on the surface of silicon wafer through the reaction between the hydroxyl end of the copolymer and native oxide layer on the wafer. In addition, an organic/inorganic hybrid surface has achieved by treating copolymer tethered Si‐substrates with SiCl₄ vapor. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3118–3122, 2006     

Polycondensation between p‐dibromobenzene and m‐dibromobenzene

NiCl₂ (bpy)‐catalyzed polycondensation between p‐dibromobenzene and m‐dibromobenzene was carried out under various conditions. With the polycondensation, a series of copolymers with number‐average molecular weights of 2400 (by gel permeation chromatography with polystyrene standards) was formed, and some samples had good solubility in organic solvents. The IR spectra and the ultraviolet spectra measured in a tetrahydrofuran (THF) solution of the copolymer showed that there were p‐phenylene and m‐phenylene units in the copolymer. According to analyses with differential scanning calorimetry, thermogravimetric analysis, and X‐rays, with an increasing molar ratio of m‐phenyl units in the copolymer, the glass‐transition temperature, the temperature of viscous flow, and the crystallizability of the polyphenylene copolymer decreased. The fluorescence spectra of the copolymer measured in a THF solution showed an emission maximum at 373–376 nm, whereas the maximum shifted to 436.6 nm for the film. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2210–2215, 2003     

ABA triblock copolymers from poly(p‐dioxanone) and poly(ethylene glycol)

Poly(p‐dioxanone)–poly(ethylene glycol)–poly(p‐dioxanone) ABA triblock copolymers (PEDO) were synthesized by ring‐opening polymerization from p‐dioxanone using poly(ethylene glycol) (PEG) with different molecular weights as macroinitiators in N₂ atmosphere. The copolymer was characterized by ¹H NMR spectroscope. The thermal behavior, crystallization, and thermal stability of these copolymers were investigated by differential scanning calorimetry and thermogravimetric measurements. The water absorption of these copolymers was also measured. The results indicated that the content and length of PEG chain have a greater effect on the properties of copolymers. This kind of biodegradable copolymer will find a potential application in biomedical materials. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1092–1097, 2006     

Synthesis of poly(octadecyl acrylate‐b‐styrene‐b‐octadecyl acrylate) triblock copolymer by atom transfer radical polymerization

The synthesis of triblock copolymer poly(octadecyl acrylate‐b‐styrene‐b‐octadecyl acrylate), using atom transfer radical polymerization (ATRP), is reported. The copolymers were prepared in two steps. First, polystyrene was synthesized by ATRP using α,α′‐dichloro‐p‐xylene/CuBr/bpy as the initiating system; Second, polystyrene was further used as macroinitiator for the ATRP of octadecyl acrylate to prepare ABA triblock copolymers in the presence of FeCl₂·4H₂O/PPh₃ in toluene. Polymers with controlled molecular weight (M_n = 17,000–23,400) and low polydispersity index value (1.33–1.44) were obtained. The relationship between molecular weight versus conversion showed a straight line. The effect of reaction temperature on polymerization was also investigated, showing a faster polymerization rate under higher temperature. The copolymers were characterized by FTIR, ¹H‐NMR, DSC, and GPC and the crystallization behavior of the copolymers was also studied. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1539–1545, 2004     

Preparation,characterization, and metal ion retention capacity of Co(II) and Ni(II) from poly(p‐HO‐ and p‐Cl‐phenylmaleimide‐co‐2‐hydroxypropylmethacrylate) using the ultra filtration technique

p‐Chlorophenylmaleimide and p‐hydroxyphenylmaleimide with 2‐hydroxypropyl methacrylate were synthesized by radical polymerization, and the metal ion retention capacity and thermal behavior of the copolymers were evaluated. The copolymers were obtained by solution radical polymerization with a 0.50 : 0.50 feed monomer ratio. The maximum retention capacity (MRC) for the removal of two metal ions, Co(II) and Ni(II) in aqueous phase were determined using the liquid‐phase polymer based retention technique. Inorganic ion interactions with the hydrophilic polymer were determined as a function of pH. The metal ion retention capacity does not depend strongly on the pH. Metal ion retention increased with an increase of pH for a copolymer composition 0.50 : 0.50. At different pH, the MRC of the poly(p‐chlorophenylmaleimide‐co‐2‐hydroxypropylmethacrylate) for Co(II) and Ni(II) ions varied from 44.1 to 48.6 mg/g and from 41.5 mg/g to 46.0 mg/g, respectively; while the MRC of poly(p‐hydroxyphenylmaleimide‐co‐2‐hydroxypropyl methacrylate) for Co(II) and Ni(II) ions varied from 28.4 to 35.6 mg/g and from 27.2 to 30.8 mg/g, respectively. The copolymers and copolymer–metal complexes were characterized by elemental analysis, FT‐IR, ¹H NMR spectroscopy, and thermal behavior. The thermal behavior of the copolymer and polymer–metal complexes were studied using differential scanning calorimetry and thermogravimetry techniques under nitrogen atmosphere. The thermal decomposition temperature and T_g were influenced by the binding‐metal ion on the copolymer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis of poly(styrene‐co‐4‐vinylpyridine) microspheres via dispersion polymerization: Effect of the concentration of 4‐vinylpyridine

Amphiphilic copolymer microspheres of poly(styrene‐co‐4‐vinylpyridine) were prepared by dispersion polymerization in an alcohol/water medium. The synthesis of poly(styrene‐co‐4‐vinylpyridine) microparticles was successfully carried out, and the latexes had a spherical morphology with good monodispersity. The degree of conversion in the early stage of polymerization decreased with increasing 4‐vinylpyridine (4VP) monomer content, but the final conversions were similar (>95%). The copolymerization rate decreased with increasing 4VP content, and a broad particle size distribution was observed with 20 wt % 4VP because of the prolonged nucleation time. With the 4VP concentration increasing, the molecular weight of the copolymer microspheres decreased, and the glass‐transition temperature of the copolymers increased; this indicated that all the copolymers were random and homogeneous. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Correlation of chemical composition and microstructure with properties of poly(ɛ‐caprolactone‐co‐p‐dioxanone) random copolymers

With the aim to develop novel biodegradable materials with good flexibility and fast degradation rate, random copolymers of ?‐caprolactone (CL) and p‐dioxanone (PDO) with a full range of compositions were synthesized in bulk using stannous octoate as the ring‐opening catalyst. The chemical composition and number average sequence lengths of CL and PDO units determined by ¹H‐NMR were used to correlate with various properties of the copolymers. Although both CL and PDO are crystalline components, only one crystalline phase could be present for each copolymer. The low limit of average block length for the copolymers that could crystallize is 3.22 for L_CL and 3.43 for L_PDO, respectively. The crystallinity and crystalline morphology of the copolymers are dependent on the crystalline component as well as its number average sequence length. Irrespective of composition, all the copolymers have good solubility in chloroform with glass transition temperature much below room temperature, implying good flexibility of the materials. The incorporation of PDO component could significantly increase the water wettability of the copolymer surfaces and thereby accelerate the degradation rate of the materials. In conclusion, flexible biodegradable polymers with adjustable degradation and crystalline properties were acquired by random copolymerization of CL and PDO, which are expected to use in tissue engineering and drug delivery fields. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2978–2986, 2013     

Synthesis of stimuli‐responsive star‐like copolymer H20‐PNIPAm‐r‐PEGMA via the ATRP copolymerization technique and its micellization in aqueous solution

A series of novel star‐like copolymers H20‐poly(N‐isopropylacrylamide)‐random‐poly(poly(ethylene glycol) methyl ether methacrylate) (H20‐PNIPAm‐r‐PEGMA), which could respond to both temperature and ionic strength stimuli in aqueous solution were synthesized by atom transfer radical polymerization. Stimuli‐response of these copolymers in aqueous solution was characterized by dynamic laser scattering (DLS), ¹H‐NMR and turbidity. In aqueous solution, these star‐like copolymers exhibited response to temperature and ionic strength with tunable low‐critical solution temperature (LCST) from 32 to 100°C. The LCST values of copolymers increased with increasing PEGMA contents, while decreased with increasing ionic strength. An interesting phenomenon, which should be a unique character of star‐like copolymer, was observed by the turbidity test of copolymer 1160. The addition of sodium chloride and increase of concentration can let copolymer 1160 behave normally, which was further confirmed by atomic force microscopy and DLS. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A novel approach for albumin determination in aqueous media by using temperature‐ and pH‐sensitive N‐isopropylacrylamide‐co‐N‐[3‐(dimethylamino)‐propyl]methacrylamide random copolymers

Random copolymers of N‐isopropylacrylamide (NIPA) and N‐[3‐(dimethylamino)propyl]methacrylamide (DMAPM) were synthesized by solution polymerization using azobisizobutyronitrile as the initiator in 1,4‐dioxane at 60°C. NIPA‐co‐DMAPM copolymer exhibited both temperature and pH sensitivity. Thermally reversible phase transitions were observed both in the acidic and the alkaline pH regions for copolymers produced with different DMAPM/NIPA feed ratios. The pH dependency of the lower critical solution temperature (LCST) was stronger for copolymers produced with higher DMAPM feed concentrations. NIPA‐co‐DMAPM random copolymer was also sensitive to the albumin concentration. In the presence of albumin, thermally irreversible phase transitions were observed in slightly acidic and neutral media. However, reversible transitions were obtained in aqueous media containing albumin at basic pH. The phase‐transition temperature of NIPA‐co‐DMAPM copolymer significantly decreased with increasing albumin concentration at both acidic and alkaline pH values. This behavior was explained by albumin binding onto the copolymer chains by means of H‐bond formation between the dimethylamino groups of the copolymer and the carboxyl groups of albumin. For a certain range of albumin concentration, the phase‐transition temperature exhibited a linear decrease with increasing albumin concentration. By utilizing this behavior, a simple albumin assay was developed. The results indicated that NIPA‐co‐DMAPM copolymer could be utilized as a new reagent for the determination of albumin concentration in the aqueous medium. The proposed method was valid for the albumin concentration range of 0–4000 μg/mL. The protein concentrations commonly utilized in biotechnological studies fall in the range of the proposed method. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2060–2071, 2002; DOI 10.1002/app.10503     

Synthesis and properties of polystyrene‐b‐poly(ethylene oxide)‐b‐polystyrene triblock copolymers

A series of well‐defined and property‐controlled polystyrene (PS)‐b‐poly(ethylene oxide) (PEO)‐b‐polystyrene (PS) triblock copolymers were synthesized by atom‐transfer radical polymerization, using 2‐bromo‐propionate‐end‐group PEO 2000 as macroinitiatators. The structure of triblock copolymers was confirmed by ¹H‐NMR and GPC. The relationship between some properties and molecular weight of copolymers was studied. It was found that glass‐transition temperature (T_g) of copolymers gradually rose and crystallinity of copolymers regularly dropped when molecular weight of copolymers increased. The copolymers showed to be amphiphilic. Stable emulsions could form in water layer of copolymer–toluene–water system and the emulsifying abilities of copolymers slightly decreased when molecular weight of copolymers increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 727–730, 2006     

Water‐soluble copolymers from functionalized monomers (sodium o‐ and p‐methacryloylaminophenylarsonate): Synthesis and characterization

Copolymers of sodium o‐methacryloylaminophenylarsonate (o‐MAPHA‐Na) 1 and p‐methacrylolylaminophenylarsonate (p‐MAPHA‐Na) 2 with sodium acrylate (AA‐Na) 3 , sodium methacrylate (AM‐Na) 4 and acrylamide (AAD) 5 were prepared by free radical polymerization in aqueous media at 70°C using potassium persulfate (K₂S₂O₈) as the initiator. The total monomer concentration was carried out at 0.5M and the feed ratio ( M₁ : M₂ ) was varied from 10 : 90 to 90 : 10 mol%. The kinetic study was carried out by dilatometric method. The copolymer compositions were calculated by arsenic content in the copolymers. The As content (ppm) was determined by atomic absorption spectrometry (AAS). The reactivity ratios (r₁, r₂) were estimated by the Kelen‐Tüdös linearization method as well as error‐in‐variables method using the computer program RREVM®. In all cases, r₁ < 1 and r₂ > 1, indicating a tendency to form random copolymers. The values suggest that the copolymers contain a larger proportion of comonomer (i.e., AA‐Na, AM‐Na, or AAD). Weight‐average molar masses (M _w) of copolymers were determined by multi‐angle light scattering. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of methyl methacrylate and N‐aryl itaconimide block copolymers via atom‐transfer radical polymerization

The paper describes the synthesis of block copolymers of methyl methacrylate (MMA) and N‐aryl itaconimides using atom‐transfer radical polymerization (ATRP) via a poly(methyl methacrylate)–Cl/CuBr/bipyridine initiating system or a reverse ATRP AIBN/FeCl₃·6H₂O/PPh₃ initiating system. Poly(methyl methacrylate) (PMMA) macroinitiator, ie with a chlorine chain‐end (PMMA‐Cl), having a predetermined molecular weight (M_n = 1.27 × 10⁴ g mol^?1) and narrow polydispersity index (PDI = 1.29) was prepared using AIBN/FeCl₃·6H₂O/PPh₃, which was then used to polymerize N‐aryl itaconimides. Increase in molecular weight with little effect on polydispersity was observed on polymerization of N‐aryl itaconimides using the PMMA‐Cl/CuBr/Bpy initiating system. Only oligomeric blocks of N‐aryl itaconimides could be incorporated in the PMMA backbone. High molecular weight copolymer with a narrow PDI (1.43) could be prepared using tosyl chloride (TsCl) as an initiator and CuBr/bipyridine as catalyst when a mixture of MMA and N‐(p‐chlorophenyl) itaconimide in the molar ratio of 0.83:0.17 was used. Thermal characterization was performed using differential scanning calorimetry (DSC) and dynamic thermogravimetry. DSC traces of the block copolymers showed two shifts in base‐line in some of the block copolymers; the first transition corresponds to the glass transition temperature of PMMA and second transition corresponds to the glass transition temperature of poly(N‐aryl itaconimides). A copolymer obtained by taking a mixture of monomers ie MMA:N‐(p‐chlorophenyl) itaconimide in the molar ratio of 0.83:0.17 showed a single glass transition temperature. Copyright © 2005 Society of Chemical Industry     

Synthesis of well‐defined comb‐like amphiphilic copolymers with protonizable units in the pendent chains: 1. Preparation of narrow polydispersity copolymers of methyl methacrylate and 2‐hydroxyethyl methacrylate by atom‐transfer radical polymerization

Well‐defined methyl methacrylate (MMA) and 2‐(trimethylsiloxy)ethyl methacrylate (Pro‐HEMA) copolymers were prepared by atom‐transfer radical polymerization(ATRP), using CuCl/2,2′‐bipyridine as catalytic system and p‐toluenesulfonyl chloride as initiator. ATRP process of MMA and Pro‐HEMA was monitored by ¹H NMR, and the kinetic curves of the MMA/Pro‐HEMA copolymerization were plotted in terms of the ¹H NMR data. At low content of Pro‐HEMA in the feed composition, the copolymerization can be well controlled with the molecular weight, polydispersity and the monomer distribution in the copolymer chain. With the increase of Pro‐HEMA content in the feed mixture, the composition of the final copolymer deviates from the composition of the feed mixture gradually, and gradient copolymers of MMA/Pro‐HEMA can be obtained. Through the hydrolysis process, well‐defined copolymers of MMA/HEMA were obtained from poly(MMA/Pro‐HEMA). Copyright © 2003 Society of Chemical Industry     

Stimuli sensitive copolymer poly(N‐tert‐butylacrylamide‐ran‐acrylamide): Synthesis and characterization

Temperature sensitive random linear and crosslinked copolymers of N‐tert‐butylacrylamide (NTBA) and acrylamide (Am) were synthesized by the solution polymerization method, using regulated dosing of comonomer Am having a higher reactivity ratio (r_Am = 1.5) than NTBA (r_NTBA = 0.5). Copolymers with varying feed ratios of NTBA and Am (80 : 20 to 20 : 80 mol %) were synthesized and characterized. For the synthesis of copolymer hydrogels, N′, N‐methylene bisacrylamide (MBA) (1.13 mol %) was used along with monomers. The effect of composition on transition properties was evaluated for the linear copolymers and their hydrogels. A definite trend was observed. The incorporation of a higher percentage of the hydrophilic comonomer Am in the structure resulted in the shifting of the transition temperature towards a higher value. The transition temperatures of the copolymers synthesized with feed compositions of 80 : 20, 70 : 30, 60 : 40, 50 : 50, 40 : 60, 30 : 70, and 20 : 80 mol % were found to be 2, 10, 19, 27, 37, 45, and 58°C, respectively. Differential scanning calorimetry (DSC) studies confirmed the formation of random copolymers. The copolymers synthesized with a monomer feed ratio of 50 : 50 with regulated dosing showed a single glass transition temperature (T_g) at 168°C, while the copolymer synthesized with full dosing of Am at the beginning of the reaction showed two T_gs, at 134 and 189°C. The copolymer samples were analyzed by Fourier transform infrared spectroscopy (FTIR) for ascertaining the composition. The composition of the copolymers followed the trend of the feed ratio, but the incorporation of NTBA in the copolymers was found to be lower than the feed ratio because of lower than quantitative yields of the reactions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 672–680, 2005     

Effects of tetramethylpolycarbonate‐block‐poly(styrene‐co‐acrylonitrile) copolymers containing various amounts of acrylonitrile on the interfacial properties of polycarbonate and poly(styrene‐co‐acrylonitrile) blends

Tetramethylpolycarbonate‐block‐poly(styrene‐co‐acrylonitrile) (TMPC‐block‐SAN) block copolymers containing various amounts of acrylonitrile (AN) were examined as compatibilizers for blends of polycarbonate (PC) with poly(styrene‐co‐acrylonitrile) (SAN) copolymers. To explore the effects of block copolymers on the compatibility of PC/SAN blends, the average diameter of the dispersed particles in the blend was measured with an image analyzer, and the interfacial properties of the blends were analyzed with an imbedded fibre retraction technique and an asymmetric double‐cantilever beam fracture test. Reduction in the average diameter of dispersed particles and effective improvement in the interfacial properties was observed by adding TMPC‐block‐SAN copolymers as compatibilizer of PC/SAN blend. TMPC‐block‐SAN copolymer was effective as a compatibilizer when the difference in the AN content of SAN copolymer and that of SAN block in TMPC‐block‐SAN copolymer was less than about 10 wt%. Copyright © 2004 Society of Chemical Industry     

Synthesis and characterization of novel rod–coil diblock copolymers of poly(methyl methacrylate) and liquid crystalline segments of poly(2,5‐bis[(4‐methoxyphenyl)oxycarbonyl] styrene)

Liquid crystalline diblock copolymers with different molecular weights and low polydispersities were synthesized by atom transfer radical polymerization of methyl methacrylate (MMA) and 2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene (MPCS) monomers. The block architecture (coil‐conformation of MMA segment and rigid‐rod of MPCS segment) of the copolymer was experimentally confirmed by a combination of ¹H nuclear magnetic resonance and gel permeation chromatograph techniques. The liquid crystalline behaviour of the copolymer was studied using differential scanning calorimetry and polarized optical microscope. It was found that the liquid crystalline behaviour was dependent on the number average molecular weight of the rigid segment. Only those copolymers with M_n(GPC) of the rigid block above 9200 g mol^?1 could form liquid crystalline phases higher than the glass transition temperature of the rigid block. The random copolymers MPCS‐co‐MMA were also synthesized by conventional free radical polymerization. The molar content of MPCS in MPCS‐co‐MMA had to be higher than 71% to maintain liquid crystalline behaviour. © 2003 Society of Chemical Industry     

Synthesis and characterization of hydrophilic copolymers of maleimide derivatives with 2‐hydroxyethyl methacrylate: electrochemical and thermal behavior

BACKGROUND: The high‐technology industries have been the driving force in the development of new synthetic polymers that combine thermal stability with specific functional properties. In this study p‐chlorophenylmaleimide, p‐hydroxyphenylmaleimide and p‐nitrophenylmaleimide (R‐PhMI) with 2‐hydroxyethyl methacrylate (HEMA) were synthesized by free radical polymerization to obtain hydrophilic polymers, in order to study the effect of the p‐chloroaryl, p‐hydroxyaryl or p‐nitroaryl group on the copolymer composition, electrochemical behavior and thermal properties. RESULTS: The thermal behavior was correlated with the copolymer composition and functional groups, maleimide derivatives, on the copolymers. Thermal decomposition temperature (TDT) and glass transition temperature (T_g) were influenced by the functional groups of R‐PhMI moiety on the copolymer. The polymers showed an electrochemically irreversible reduction process under the conditions tested. CONCLUSION: Poly[(p‐chloromaleimide)‐co‐(2‐hydroxyethyl methacrylate)] copolymer shows a higher TDT than poly[(p‐hydroxymaleimide)‐co‐(2‐hydroxyethyl methacrylate)] or poly[(p‐nitromaleimide)‐co‐(2‐hydroxyethyl methacrylate)] (NPHE). T_g decreases in going from nitro to hydroxyl to chloro groups. The NPHE copolymer shows a lower stability, losing weight at 200 °C. The NPHE copolymer shows a well‐defined reduction wave which is similar to those of the other copolymers and it also shows an additional quasi‐reversible reduction wave corresponding to the nitrobenzene group. Copyright © 2009 Society of Chemical Industry