Synthesis and nitrosation of processible copolymers from pyrrole and ethylaniline

A series of copolymers were prepared by an oxidative polymerization of pyrrole (PY) and 2-ethylaniline (EA) in HCl. The polymerization process was followed by tracking open-circuit potential and temperature of the reaction solutions. The fine particles of the PY/EA copolymers obtained in situ were further N-nitrosated for the first time in order to improve their solubility. The size, structure, and properties of the fine particles and their N-nitroso products were systematically characterized by laser particle size analyzer, FTIR, UV-vis, GPC, solution casting, and TG techniques. It is found that both the open-circuit potential and temperature of the solutions exhibit a maximum during the copolymerization, while the particle size of the copolymers will decrease monotonically with prolongating polymerization time or doping. Both the polymerization yield and molecular weight of the copolymers exhibit a minimum with PY/EA ratio, indicating a mutual retarding effect between the PY and EA monomers. The top potential and top temperature of the copolymerization as well as the particle size and its distribution, solubility, film-forming ability, electroconductivity, and thermostability of the copolymers all depend significantly on the PY/EA ratio. The PY/EA copolymers have good solubility in the solvents with the solubility parameter from 23 to 27 J^1/2/cm^3/2, dielectric constant greater than 12 and polarity index from 6.4 to 7.4 and their solubility becomes further better with increasing EA content. The N-nitrosation of copolymers can also improve their solubility in polar solvents furthermore. The copolymers with PY content of less than 30 mol% in NMP and THF exhibit good thin-film formability. The copolymer films become smoother and tougher with increasing EA content and by N-nitrosation. With increasing PY content, the decomposition temperature, maximum decomposition rate, char yield at 500 °C, and activation energy all decrease but decomposition order increases. The temperature at the maximum weight-loss rate of the copolymers has a maximum at the PY/EA molar ratio of 30/70. These results suggest that the polymer obtained is a real copolymer containing two comonomer units.     

Facile synthesis of oxidative copolymers from aminoquinoline and anisidine

Oxidative copolymerization of 8-aminoquinoline (AQ) and o-anisidine (AS) using ammonium persulfate as oxidant was studied under various polymerization conditions and fine and uniform copolymer particles of several micrometers, determined by laser particle size and atomic force microscopic analyses, were synthesized simply. The polymerization yield, molecular weight, solubility, electroconductivity, and thermostability of the copolymers were systematically studied by changing the comonomer ratio, polymerization temperature, monomer/oxidant ratio, and acidic medium. Single chain configuration of the copolymers with various AQ/AS ratios was simulated and well related to the intrinsic viscosity. The macromolecular structure of the resulting copolymers was wholly characterized by elementary analysis, IR, UV-vis, high-resolution ¹H NMR, and solid-state high-resolution ¹³C NMR. The results show that the oxidative copolymerization of AQ and AS is exothermic. All copolymers are totally soluble in H₂SO₄, HCOOH, m-cresol but their solubility in other solvents depends significantly on the comonomer ratio, and also on the polymerization conditions. The oxidative polymer obtained is a real copolymer containing AQ and AS units rather than a mixture of two homopolymers. The AQ content calculated based on the ¹H NMR spectra of the copolymers is slightly higher than feed AQ content when feed AQ content is lower than 70 mol%. However, the AQ content calculated based on the ¹³C NMR and elementary analyses is lower than the feed AQ content when the AQ feed content is higher than 50 mol%. A peculiar dependency of molecular weight and electroconductivity of the copolymers on the AQ/AS ratio was observed. The decomposition temperature of the copolymers rises with increasing AQ content. Therefore, the thermostability of the copolymers increases with increasing AQ content due to its high aromaticity.     

Preparation and solubility of a partial ladder copolymer from p-phenylenediamine and o-phenetidine

A series of copolymers were synthesized by chemically oxidative polymerization of p-phenylenediamine (PPD) and o-phenetidine (PHT) in acidic aqueous media. The polymerization yield, intrinsic viscosity, and solubility of the copolymers were comprehensively studied by changing the comonomer ratio, polymerization time and temperature, oxidant, monomer/oxidant ratio, and acidic medium. As-prepared fine powder of the PPD/PHT copolymers was characterized by FT-IR, UV-vis, high-resolution ¹H-NMR, and DSC techniques. A circular dichroism technique was firstly used to characterize the macromolecular structure of the copolymers. The results showed that the oxidative copolymerization from PPD and PHT is exothermic and the resulting copolymers exhibit an enhanced solubility in most of the organic solvents as compared with poly(p-phenylenediamine), sometimes also with poly(o-phenetidine). The polymer obtained is a real copolymer containing PPD and PHT units, and the actual PPD/PHT ratio calculated by ¹H-NMR spectra of the polymers is very close to the feed ratio. The DSC measurement indicates that the copolymers are amorphous and chemically instable at elevated temperature.     

A soluble ladder copolymer from m-phenylenediamine and ethoxyaniline

A series of partial ladder copolymers were synthesized by chemically oxidative polymerization of m-phenylenediamine (MPD) and o-ethoxyaniline (EOA) using inorganic oxidants in inorganic acidic aqueous media. The polymerization yield, intrinsic viscosity, solubility, and thermal property of the copolymers were systematically studied by changing the comonomer ratio, initial polymerization temperature, polymerization time, oxidant, monomer/oxidant ratio, and acidic medium. As-prepared fine powder of the MPD/EOA copolymers was characterized by IR, UV-vis, and high-resolution ¹H NMR spectroscopies and DSC. Circular dichroism technique was firstly used to characterize chain structure of the copolymers. The results showed that the oxidative polymerization from MPD and EOA is exothermic and the resulting copolymers exhibit a remarkably enhanced solubility in all of the organic and inorganic solvents chosen as compared with totally insoluble MPD homopolymer. The polymers obtained by the oxidative polymerization are real copolymers containing MPD and EOA units but do not contain MPD and EOA homopolymers based on a careful solubility comparison. The actual MPD/EOA molar ratio calculated based on ¹H NMR spectra of the polymers is different from element analysis results. Element analysis indicated that denitrogenation happens during the polymerization linkage among MPD units and the structure consisting of MPD units is different from that reported. The ladder degree of the copolymers might be monitored by controlling MPD/EOA ratio. The DSC measurement indicates that the copolymers do not exhibit melt transition.     

Synthesis of electrically conducting copolymers of aniline with o/m-amino benzoic acid by an inverse emulsion pathway

Copolymers of aniline and ortho/meta-amino benzoic acid were synthesized by chemical polymerization using an inverse emulsion pathway. The copolymers are soluble in organic solvents, and the solubility increases with the amino benzoic acid content in the feed. The reaction conditions were optimized with emphasis on high yield and relatively good conductivity (2.5×10⁻¹ S cm⁻¹). The copolymers were characterized by a number of techniques including UV-vis, FT-IR, FT-Raman, EPR and NMR spectroscopy, thermal analysis, SEM and conductivity. The influence of the carboxylic acid group ring substituent on the copolymers is investigated. The spectral studies reveal that the amino benzoic acid groups restrict the conjugation along the polymer chain. The SEM micrographs of the copolymers reveal regions of amorphous and crystalline domain. Thermal studies indicate a marginally higher thermal stability for poly(aniline-co-m-amino benzoic acid) compared to poly(aniline-co-o-amino benzoic acid).     

Considerations of polymerization method and molecular weight for proton-conducting poly(p-phenylene) derivatives

Ni(0)-catalyzed coupling polymerization of 2,5-dichloro-4′-phenoxybenzophenone was investigated by varying the ligand and coligand, temperature, reaction time, and solvent. The weight-average molecular weight (M_w) of poly(4-phenoxybenzoyl-1,4-phenylene)s (PPBPs) could be controlled by the polymerization conditions and reached a maximum of 4.4 × 10⁵ g mol⁻¹. Sulfonated PPBPs (S-PPBPs) with various M_ws were prepared with sulfuric acid to study the effect of molecular weight on the chemical and electrical properties of PPBP-based electrolytes. The strong molecular interactions in S-PPBP provided an ion exchange capacity of 2.9 meq g⁻¹ without loss of high mechanical properties. High molecular weight S-PPBPs had more desirable properties for fuel cell applications. While the swelling ratios and hydration numbers of S-PPBPs decreased with increasing molecular weight, the mechanical strength, proton conductivity, and fuel cell performance increased. S-PPBP also showed anisotropic behavior in the swelling and proton conductivity; such behavior is caused by the rigid-rod nature and the liquid-crystal structure.     

Controllable synthesis of poly(N-vinylpyrrolidone) and its block copolymers by atom transfer radical polymerization

At room temperature atom transfer radical polymerization (ATRP) of N-vinylpyrrolidone (NVP) was carried out using 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacyclo-tetradecane (Me₆Cyclam) as ligand in 1,4-dioxane/isopropanol mixture. Methyl 2-chloropropionate (MCP) and copper(I) chloride were used as initiator and catalyst, respectively. The polymerization of NVP via ATRP could be mediated by the addition of CuCl₂. The resultant poly(N-vinylpyrrolidone) (PNVP) has high conversion of up to 65% in 3 h, a controlled molecular weight close to the theoretical values and narrow molecular weight distribution between 1.2 and 1.3. The living nature of the ATRP for NVP was confirmed by the experiments of PNVP chain extension. With PNVP-Cl as macroinitiator and N-methacryloyl-N′-(α-naphthyl)thiourea (MANTU) as a hydrophobic monomer, novel fluorescent amphiphilic copolymers poly(N-vinylpyrrolidone)-b-poly(N-methacryloyl-N′-(α-naphthyl)thiourea) (PNVP-b-PMANTU) were synthesized by ATRP. PNVP-b-PMANTU copolymers were characterized by ¹H NMR, GPC-MALLS and fluorescence measurements. The results revealed that PNVP-b-PMANTU presented a blocky architecture.     

Preparation and identification of a soluble copolymer from pyrrole and o-toluidine

A series of copolymers were prepared by chemically oxidative polymerization of pyrrole (PY) and ortho-toluidine (OT) in HCl aqueous medium. The yield, intrinsic viscosity, and solubility of the copolymers were studied by changing the monomer molar ratio. The resulting PY/OT copolymers were identified by FTIR, ¹H–NMR, DSC, and WAXD techniques. The experimental results showed that the oxidative polymerization of pyrrole and o-toluidine is exothermic and the resulting polymers exhibit an enhanced solubility in most organic solvents compared with that of pyrrole homopolymer. The polymer obtained is a real and amorphous copolymer containing pyrrole and o-toluidine units. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 510–518, 2001     

Facile synthesis of highly soluble copolymers and sub-micrometer particles from ethylaniline with anisidine and sulfoanisidine

Two series of copolymers were synthesized by an oxidative polymerization of 2-ethylaniline (EA) with 2-anisidine (AS) or 5-sulfonic-2-anisidine (SA) for a detailed comparative study between EA/SA and EA/AS copolymers. The preparation, structure, and properties of the copolymers were systematically studied by FT-IR, high-resolution ¹H NMR, UV-vis, elementary analysis, GPC, laser particle size analysis, atomic force microscope, and thermogravimetry. Significant dependences of the yield, molecular weight, solubility, and thermostability of the copolymer particles on the comonomer ratio and oxidant/monomer ratio have been observed. The molecular weight increases continuously with increasing EA content in the two copolymers. Quinoid structures favor on the EA units in EA/AS copolymers with the whole oxidation rate of larger than 0.5 in the molecular chain. Although the EA/AS copolymers exhibit only external doping, the EA/SA copolymers exhibit not only external doping on EA units but also self-doping on SA units. The monomer reactivity increases in the order of EA≤SA<AS. The size and its distribution of the particles are highly dependent on polymerization time and comonomer ratio. The sub-micrometer particles with the smallest diameter of 120 nm are easily prepared by an in situ EA/SA (70/30) polymerization. A relationship between the particle diameter and macromolecular steric model is founded. A new simple method of preparing sub-micrometer particles of aniline derivative polymers without adscititious stabilizer is established. A possible formation mechanism of the sub-micrometer particles during a non-emulsion EA/SA polymerization is proposed. The polymer particles obtained are completely soluble in many solvents and exhibit a very good film-forming ability. A regular variation of the thermostable characteristics of the copolymers with comonomer ratio is found and a three-step process of the thermal degradation is assigned.     

Synthesis of thermosensitive polymers containing sugar branches

Copolymers of 6‐O‐vinyladipoyl‐D ‐glucose (VAG) and N‐isopropyl acrylamide (NIPAm) were synthesized by radical polymerization. The number‐average molecular weights of the copolymers were 3 × 10⁴ ≈ 6 × 10⁴. The observed segment composition of copolymers at the feed molar ratio (VAG 25/NIPAm 75) was VAG 10/NIPAm 90. The polymerization rate of the VAG monomer was slower than that of the NIPAm monomer. The lower critical‐solution temperature of copolymers measured with a light‐scattering photometer and a differential scanning calorimeter increased with increasing VAG segment composition. The increase in transition temperature was accompanied by a decrease in transition heat. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 384–387, 2001     

Chemical synthesis,characterization, and properties of conducting copolymers of imidazole and carbazole

Conducting copolymers of imidazole and carbazole were chemically synthesized in various molar ratios of the imidazole and carbazole by chemical oxidative polymerization in acetonitrile medium using ammonium persulphate as oxidant. The selection and composition of solvent, concentration of the monomer, polymerization time, and temperature were optimized to obtain better quality and yield of the copolymers. The synthesized conducting copolymers were characterized by various techniques such as UV–visible, Fourier transform infrared, ¹H‐NMR, and X‐ray diffraction spectroscopy. The solubility of the copolymers was tested in various solvents. Their conductivity was tested at various temperatures. The thermodynamic stability of the copolymers was examined by differential scanning colorimetric and thermogravimetric analysis. The copolymers show comparatively higher conductivity, better solubility, and higher thermal stability than the homopolymer poly(carbazole) and lower than that of poly(imidazole). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of biodegradable poly(trans-4-hydroxy-N-benzyloxycarbonyl-l-proline)-block-poly(ε-caprolactone) copolymers and micellar characterizations

A series of novel types of diblock poly(trans-4-hydroxy-N-benzyloxycarbonyl-l-proline)-block-poly(ε-caprolactone) (PHpr10-b-PCL) copolymers were synthesized by ring-opening polymerization from macroinitiator poly(trans-4-hydroxy-N-benzyloxycarbonyl-l-proline) (PHpr10) and ε-caprolactone (ε-CL) in the presence of organocatalyst dl-lactic acid (dl-LA). The M_n of the copolymers increased from 3370 to 19,040 g mol⁻¹ with the molar ratio (10-100) of ε-CL to PHpr10. These products were characterized by differential scanning calorimetry (DSC), ¹H NMR, and gel permeation chromatography. According to DSC, the glass-transition temperature (T_g) of the diblock copolymers depend on the molar ratio of monomer/initiator that were added. The hydrolytic degradation behavior of PHpr-b-PCLs was evaluated from weight-loss measurements and the change of M_n and M_w/M_n. With higher PCL contents resulted in a slower weight loss, while having a higher molecular weight loss percentage. Their micellar characteristics in an aqueous phase were investigated by fluorescence spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). The block copolymers formed micelles in the aqueous phase with critical micelle concentrations (CMCs) in the range of 1.33-4.22 mg L⁻¹. The micelles exhibited a spindly shape and showed a narrow monodisperse size distribution. The obtained micelles have a relatively high drug-loading of about 26% when the feed weight ratio of amitriptyline hydrochloride (AM) to polymer was 1/1. An increase of molecular weight and hydrophobic components in copolymers produced a higher CMC value and greater loading efficiencies were observed.     

Synthesis,characterization, and properties of amphiphilic poly(ethyl acrylate) with uniform polyoxyethylene grafts

Amphiphilic copolymers of ethyl acrylate (EA) with uniform polyoxyethylene (PEO) grafts were synthesized by copolymerization of EA with methacrylate terminated PEO macromer in benzene using azobisisobutyronitrile as the initiator. The effects of the molecular weight of the macromers, the charging weight ratio of the macromer to EA, the total monomer concentration, and the amount of initiator on the grafting efficiency (GE) were reported as was the molecular weight of the copolymers. The highest GE reached to above 90% and the molecular weight of the copolymers varied from (5–15) × 10⁴. The reactivity ratio of EA with the macromer was determined to be 0.83. The graft copolymers were purified with extractions and the purified products were characterized with IR, ¹H‐NMR, gel permeation chromatography, differential scanning calorimetry, and membrane osmometry. The average grafting number of the copolymer varied from 2 to 11. The glass‐transition temperature of the poly(EA) in the copolymer was increased because of the partial compatibility of the two components. The crystalline property, emulsifying property, and dilute solution viscosity of the graft copolymers, as well as ionic conductivity of their complexes with alkali metal salts, were studied. The emulsifying volume decreased with the increasing molecular weight of the PEO grafts. The addition of NaOH to the emulsion affected the emulsifying volume only slightly, whereas the addition of HCl changed the oil in water type emulsion into a water in oil type. The conductivity of the LiClO₄ complex of the copolymer with an oxyethylene/Li ratio of 20 reached 3.7 × 10^?5 S/cm at 27°C. The lower the crystallinity of the complex, the higher was the conductivity. The dilute solution viscosity showed the existence of intramolecular microphase separation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 903–912, 2001     

Synthesis of amphiphilic ethyl cellulose grafting poly(acrylic acid) copolymers and their self-assembly morphologies in water

Amphiphilic ethyl cellulose (EC)-g-poly(acrylic acid) (PAA) copolymers were synthesized by atom transfer radical polymerization (ATRP). Firstly, ethyl cellulose macro-initiators with the degree of the 2-bromoisobutyryl substitution of 0.04 and 0.25 synthesized by the esterification of the hydroxyl groups remained in EC macromolecular chains and the 2-bromoisobutyryl bromides. Secondly, tert-butyl acrylate was polymerized by ATRP with the ethyl cellulose macro-initiator and EC-g-PtBA copolymers were prepared. Finally, the EC-g-PAA copolymers were prepared by hydrolyzing tert-butyl group of the EC-g-PtBA copolymers. The grafting copolymers were characterized by means of GPC, ¹H NMR and FTIR spectroscopies. The molecular weight of graft copolymers increased during the polymerization and the polydispersity was low. A kinetic study showed that the polymerization was first-order. Meanwhile, EC-g-PAA copolymers were self-assembled to micelles or particles with diameters of 5 nm and 100 nm in water (pH = 10) when the concentration was 1.0 mg/ml.     

Phosphonic acid-containing homo-, AB and BAB block copolymers via ATRP designed for fuel cell applications

The synthesis of various block copolymers containing phosphonic acid moieties is described. Poly(styrene)/PDEVBP AB block copolymers were obtained by atom transfer radical polymerization (ATRP) of diethyl p-vinylbenzyl phosphonate (PDEVBP). Subsequently, BAB block copolymers with tailored architecture composed of the phosphonated monomer and poly(ether ether ketone) were obtained by a combination of polycondensation chemistry and ATRP. The quantitative deprotection of the ethyl phosphonates led to the corresponding free phosphonic acids, which can be applied as polymer electrolyte membranes for fuel cells. In addition, all materials showed high thermal stability. The proton conductivity properties of the ionomers were investigated. The phosphonic acid-containing (co)polymers exhibited a linear increase of the conductivity with the temperature with a maximum value of 4.5 × 10⁻⁴ S/cm in anhydrous conditions.     

Synthesis and characterization of novel fluoropolymers containing sulfonyl and perfluorocyclobutyl units

A novel sulfonyl-containing monomer, 4,4′-sulfonyl-bis(trifluorovinyloxy)biphenyl, and the resulting fluoropolymers with good thermal stability have been prepared. The monomer was synthesized by two steps using 4,4′-sulfonyldiphenol as starting material and characterized by FT-IR, ¹H NMR, ¹³C NMR, ¹⁹F NMR and element analysis in detail. Fluoropolymers containing sulfonyl and perfluorocyclobutyl units were prepared by different polymerization methods. A series of fluoropolymers with higher molecular weights were obtained by solution polymerization in diphenyl ether. The molecular weight is dependent on the polymerization time, polymerization temperature and the concentration of the monomer. The resulting polymers show excellent solubility in conventional solvents and good thermal stability with a high decomposition temperature about 500 °C measured by TGA.     

Synthesis of well-defined and near narrow-distribution diblock copolymers comprising PMMA and PDMAEMA via oxyanion-initiated polymerization

In this paper, the possibilities offered by oxyanion-initiated polymerization were exploited to tailor well-defined and near narrow-distribution poly[(dimethylamino)ethyl methacrylate]-b-poly(methyl methacrylate) (PDMAEMA-b-PMMA) AB or BA diblock copolymers that were initiated by potassium benzyl alcoholate (BzOK) and controlled by the sequential addition of the alternative monomers. To clarify the living mechanism for MMA and DMAEMA, a series of MMA and DMAEMA homopolymers with near narrow molecular weight distribution were prepared in our laboratory, respectively. If not quenched, the first living moiety could be subsequently used to yield block copolymers BzO-PDMAEMA-b-PMMA with adding the second feed of monomer to the living system. Using reverse succeeding addition of monomers, another benzyloxy-capped diblock copolymer, i.e. BzO-PMMA-b-PDMAEMA was obtained. The thorough characterization of all these diblock copolymers was investigated from ¹H NMR measurement. The results indicated that the expected molecular structures have been obtained with a good correlation between original monomer-to-initiator molar ratios. GPC analysis showed that PDMAEMA homopolymer and the above mentioned two block copolymers possessed narrow molecular weight distribution in the range of 1.15-1.34, while PMMA homopolymer had a little broad molecular weight distribution of 1.29-1.60. This study shows further evidence that oxyanion-initiated polymerization is a control/‘living’ process, not only suitable for tertiary amino-substituted methacrylates, but also for methyl methacrylate. The critical micelle concentration (cmc) of the diblock copolymer BzO-PDMAEMA-b-PMMA in aqueous solution was attained by surface tension measurement. The effects of different lengths of two segments and pH values on the behavior of solution were investigated.     

Thermo-, and pH dual-responsive poly(N-vinylimidazole): Preparation,characterization and its switchable catalytic activity

A monomer, 2-(isobutyramido)-3-methylbutyl methacrylate (IMMA) was synthesized through a two-step reaction. When a few of IMMA (less than 4 mol%) was copolymerized with N-vinylimidazole (VIm) under free radical polymerization condition, water-soluble P(VIm-co-IMMA) copolymers were obtained. Their structural information was verified and interpreted from ¹H NMR, FTIR and GPC. Kinetic analyses from ¹H NMR demonstrated that one-batch addition of IMMA into the polymerization system led to an inhomogeneous distribution of IMMA units in the copolymers, whereas homogeneous distribution of IMMA units in the copolymers could be obtained through the portion-wise addition of IMMA monomer. The thermal properties of such copolymers were measured by DSC. Compared with PVIm homopolymer, the few IMMA units in the P(VIm-co-IMMA) copolymer had little influence on the T_g values. The obtained P(VIm-co-IMMA) copolymers were thermoresponsive in water, and their phase transition temperatures could be efficiently raised through reducing the IMMA content in the copolymers, raising the addition times of IMMA monomers or lowering the pH of media. Dynamic light scattering analysis showed that unlike the traditional thermoresponsive linear polymers, obvious size shrinkage around the phase transition temperature could not be observed in such P(VIm-co-IMMA) copolymers. Such copolymers could be used as smart organocatalysts in the hydrolysis of p-nitrophenyl acetate. Below the phase transition temperature the reaction rate followed the Arrhenius law, but above the phase transition temperature the reaction rate increased much slower than the prediction from the Arrhenius law. Moreover, the catalytic transition temperature could be tuned through utilizing the P(VIm-co-IMMA) copolymers with different phase transition temperature. The mechanism was discussed accordingly.     

Preparation of hyperbranched copolymers of maleimide inimer and styrene by ATRP

Novel hyperbranched copolymers were prepared by the atom transfer radical copolymerization of N-(4-α-bromobutyryloxy phenyl) maleimide (BBPMI) with styrene in 1-methyl-2-pyrrolidone (NMP) using the complex of CuBr/2,2′-bipyridine as catalyst. The copolymerization behavior was investigated by comparison of the conversion of double bond of BBPMI determined by ¹H NMR with that of styrene. The hyperbranched structure of resulting copolymers was verified by gel permeation chromatography (GPC) coupled with multi-angle laser light scattering (MALLS). The influences of dosage of catalyst and monomer ratio on the polymerization rate and structure of the resulting polymers were also investigated. The glass transition temperature of the resulting hyperbranched copolymer increases with increasing mole fraction of BBPMI, f_BBPMI. The resulting copolymers exhibit improved solubility in organic solvents; however, they show lower thermal stabilities than their linear analogues.     

Living cationic random copolymerization of β-pinene and isobutylene with 1-phenylethyl chloride/TiCl4/Ti(OiPr)4/nBu4NCl

The first example of living cationic random copolymerization of β-pinene and isobutylene was achieved with 1-phenylethyl chloride/TiCl₄/Ti(OiPr)₄/nBu₄NCl (TiCl₄/Ti(OiPr)₄ mole ratio: 3/1) initiating system in CH₂Cl₂ at −40 °C. β-Pinene and isobutylene was consumed at almost the same rate, suggesting that the two monomers exhibit almost equal reactivity. At any monomer feed ratio, the number-average molecular weight (M_n) of the copolymers increased in direct proportion to the total monomer conversion, and the molecular weight distribution was relatively narrow (M_w/M_n=1.1-1.2) throughout the reaction. The reactivity ratios determined by the Kelen-Tüdõs method were rβ-pinene=1.1 and r_isobutylene=0.89, which indicated that the composition of copolymer is approximately identical to the monomer feed ratio. The analysis of the structure and sequence distribution of the copolymers by ¹H NMR spectroscopy further confirmed that perfectly random copolymers were obtained by this living cationic polymerization system. The glass transition temperatures of the copolymers obtained with varying monomer compositions were also determined by DSC method.