Difunctional Poly Research Articles

In situ Fourier transform near infrared spectroscopy monitoring of copper mediated living radical polymerization

AbstractIn situ Fourier transform near infrared (FTNIR) spectroscopy was successfully used to monitor monomer conversion during copper mediated living radical polymerization with N‐(n‐propyl)‐2‐pyridylmethanimine as a ligand. The conversion of vinyl protons in methacrylic monomers (methyl methacrylate, butyl methacrylate, and N‐hydroxysuccinimide methacrylate) to methylene protons in the polymer was monitored with an inert fiber‐optic probe. The monitoring of a poly(butyl methacrylate‐b‐methyl methacrylate‐b‐butyl methacrylate) triblock copolymer has also been reported with difunctional poly(methyl methacrylate) as a macroinitiator. In all cases FTNIR results correlated excellently with those obtained by 1H NMR. On‐line near infrared (NIR) measurement was found to be more accurate because it provided many more data points and avoided sampling during the polymerization reaction. It also allowed the determination of kinetic parameters with, for example, the calculation of an apparent first‐order rate constant. All the results suggest that FTNIR spectroscopy is a valuable tool to assess kinetic data. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4933–4940, 2004

Well-Defined Amphiphilic Thermosensitive Copolymers Based on Poly(ethylene glycol monomethacrylate) and Methyl Methacrylate Prepared by Atom Transfer Radical Polymerization

Amphiphilic homopolymers of the hydroxy-functional macromonomer poly(ethylene glycol) monomethacrylate (PEGMA) and its copolymers with methyl methacrylate (MMA) were prepared by atom transfer radical polymerization. Commercially available PEGMA (Aldrich) contains nonfunctional poly(ethylene glycol) (PEG), monofunctional PEGMA, and difunctional poly(ethylene glycol) dimethacrylate (PEGDMA) in a 1:3:1 ratio as analyzed by HPLC. A solvent extraction procedure yielded a PEGMA enriched mixture (PEG:PEG-MA:PEGDMA = 5:92:3) with PEGMA Mn values of 480 and 410 Da based on HPLC and 1H NMR, respectively. ATRP homopolymerization of this purified PEGMA in the hydroxyl-bearing solvents, cyclohexanol and ethanol (ε = 16.4 and 25.3, respectively), yielded well-defined homopolymers (Mw/Mn < 1.1). On the other hand, ATRP copolymerizations with MMA (PEGMA content = 10, 18, 24, 30, and 40 mol %) yielded best results in non-hydrogen-bonding diphenyl ether (ε = 3.37). The homopolymer and copolymers containing more than 24 mol % (57 wt %) PEGMA were water-soluble and exhibited sharp lower critical solution temperatures (LCST) that increased with increasing PEGMA content as expected. Unlike similar PEGMA-based amphiphilic copolymers prepared by conventional free radical polymerizations, the ATR polymerizations reported here proceeded to high conversions (60−100%) and yielded well-defined polymers (Mw/Mn = 1.1−1.15) with no gel fraction that remained linear and water-soluble after storage in ambient conditions for several months.

Synthesis of ABABA pentablock copolymers via copper mediated living radical polymerisation

In this work, the syntheses of poly(butyl methacrylate- b-methyl methacrylate- b-butyl methacrylate) triblock copolymer and poly(methyl methacrylate- b-butyl methacrylate- b-methyl methacrylate- b-butyl methacrylate- b-methyl methacrylate) pentablock copolymers using copper mediated living radical polymerisation are reported. Living radical polymerisations were performed using the system Cu IBr/ N-( n-propyl)-2-pyridylmethanimine as catalyst in conjunction with a difunctional initiator, the 1,4-(2 ′-bromo-2 ′-methylpropionoto)benzene ( 1). The syntheses of poly(MMA), poly(BMA- b-MMA- b-BMA) and poly(MMA- b-BMA- b-MMA- b-BMA- b-MMA) are described in detail using 1H NMR spectroscopy and size exclusion chromatography. The living behaviour and the blocking efficiency of these polymerisations were investigated in each case. Difunctional initiator, 1, based on hydroquinone was synthesised and fully characterised and subsequently used to give difunctional poly(methyl methacrylate) macroinitiators with molecular weights up to 54,000 g mol −1 and polydispersity between 1.07 and 1.32; molecular weights were close to the theoretical values. The difunctional macroinitiators were used to reinitiate butyl methacrylate to give triblock copolymers of M n between 17,500 and 45,700 g mol −1. Polydispersities remained narrow below 25,000 g mol −1 but broadened at higher masses. The difunctional triblock macroinitiators were subsequently used to reinitiate methyl methacrylate to give ABABA pentablock copolymers with M n up to 37,000 g mol −1 with polydispersity=1.13. Under certain conditions radical–radical reaction led to a broadening of polydispersity index.

Synthesis and Characterization of Poly(styrene-b-n-butyl acrylate-b-styrene) Triblock Copolymers Using a Dialkoxyamine as Initiator

This study investigates the ability of a novel difunctional alkoxyamine based on N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide (SG1) to serve as initiator for the controlled radical polymerization of styrene (S) and n-butyl acrylate (nBuA). The efficiency of this initiator was checked using three different methods. After we set up the conditions best suited to the synthesis of perfectly difunctional poly(n-butyl acrylate) (PnBuA) samples, well-defined poly(styrene-b-n-butyl acrylate-b-styrene) triblock copolymers could be obtained by sequential polymerization of the corresponding monomers. However, a loss of control of the targeted structure was observed whenever the conversion of styrene exceeded 40%.

Controlled/Living Radical Polymerization in the Undergraduate Laboratories. 1. Using ATRP to Prepare Block and Statistical Copolymers of n-Butyl Acrylate and Styrene

A simple method of preparing well-defined (co)polymers has been developed for application in an advanced undergraduate laboratory. The method utilizes atom transfer radical polymerization (ATRP), a controlled/living radical polymerization, to prepare difunctional poly(n-butyl acrylate) with bromine end groups, which is chain-extended with styrene to yield an ABA triblock copolymer. Simultaneously, a statistical copolymer of the two monomers is prepared for comparison. The two copolymers are isolated and compositions and molecular weights are determined using 1H NMR and SEC, respectively. Optional additions to the experiment include performing a kinetic analysis of the homopolymerization using GC and SEC, and possibly comparing the results to those expected for conventional radical polymerization. Material differences in the copolymers can be observed qualitatively or measured using thermal or mechanical analysis. The lab is designed in such a way that several parts of the whole can be used to emphasize different areas of polymer science. A more synthetic course such as the organic synthesis lab can opt to investigate only the kinetic and composition analyses, whereas an engineering or materials science course may pursue more rigorous analysis of the materials' properties. Results included here are intended for application in an organic synthesis laboratory course.

ABC Triblock Copolymers Prepared Using Atom Transfer Radical Polymerization Techniques

Triblock copolymers (or, alternatively, terpolymers) of the type ABC, where A, B, and C represent distinct blocks based on different monomers, have been prepared using atom transfer radical polymerization (ATRP) techniques. Various macroinitiators, including mono- and difunctional poly(tert-butyl acrylate), difunctional poly(styrene), and trifunctional p(St), were prepared and used for block copolymerizations with different monomers, including methyl acrylate, methyl methacrylate, and vinylpyridine. The block copolymers were characterized by gel permeation chromatography to determine chain end functionality and by 1H NMR to measure the final composition of the block copolymers. Additionally, guidelines are presented for preparing block copolymers using ATRP techniques. Topics addressed include approaches to retaining the chain end functionality, achieving a high blocking efficiency, as well as strategies to maintain control over the ATRP reaction.

Polyurethaneurea/Vinyl Polymer Hybrid Aqueous Dispersions Based on Renewable Material

A series of polyurethaneurea-vinyl polymer (PUA) hybrid aqueous dispersions were synthesized from castor oil and/or difunctional poly(oxypropylene) polyol (GE-210, M(n) = 1000), butyl acrylate, and styrene. The effect of hybrid between the polyurethaneurea (PUU) and vinyl polymer (PA) on the morphologies and the mechanical properties for these PUA films was examined and studied. The experimental results showed that there was appreciable miscibility between the PUU and PA phases for the PUA prepared with GE-210, giving rise to less ordered hard segments in PUU and resulting in lowering of some mechanical properties compared with those of pure PUU synthesized with GE-210. For PUA based on castor oil, the compatibility between the PUU and PA phases was also observed, although there was a network structure in the system. Moreover, the particle-accumulation morphology during the film formation process for this PUA system disappeared, but this behavior was found for a similar PUU. In this case, a great improvement of mechanical properties for such a PUA specimen was observed. The other PUA specimens with high content of castor oil exhibit excellent comprehensive mechanical properties, resulting from the reinforcement of cross-linked PUU phase existing in the systems.

Development of novel attachable initiators for atom transfer radical polymerization. Synthesis of block and graft copolymers from poly(dimethylsiloxane) macroinitiators

The synthesis of poly(styrene-dimethylsiloxane) block and graft copolymers is described. Commercially available difunctional poly(dimethylsiloxane) (PDMS) containing either vinylsilyl or hydrosilyl terminal species was reacted with the corresponding hydrosilyl or vinylsilyl attachable initiators containing the benzyl chloride species. The attachment of the initiators to PDMS was achieved by hydrosilation in the presence of a platinum(0) catalyst. The terminal benzyl chloride groups were then used as initiators for atom transfer radical polymerization (ATRP) to produce block copolymers. Using this technique, triblock copolymers consisting of a PDMS centre block and polystyrene terminal blocks were synthesized. A similar process was also used to produce graft copolymers of polystyrene from a PDMS backbone.

Amphiphilic core–shell nanospheres obtained by intramicellar shell crosslinking of polymer micelles with poly(ethylene oxide) linkers

Intramicellar crosslinking of the polymer chains within the shells of polystyrene-b-poly(acrylic acid) micelles by reaction with difunctional poly(ethylene oxide) afforded unimolecular amphiphilic core–shell nanospheres (50 nm hydrodynamic radius); the resulting surface hydrogel layer gives an approximate fivefold increase of particle volume from the dry state to aqueous solution.

Synthesis of Novel Biodegradable Poly(Ester-Anhydride)s

Poly(ϵ-caprolactone)s containing one and variable numbers of anhydride functions along the polymer backbone were synthesized and characterized. The inclusion of a single anhydride unit involved the coupling of monofunctional carboxylic acid-terminated prepolymers using diphenyl chlorophosphate. The prepolymers were produced using stannous octoate as catalyst and ethanol as the initiator, yielding mono-functional hydroxyl-terminated intermediates which were reacted with succinic anhydride in the presence of 1-methylimidazole. Diphenyl chlorophosphate was then added to a solution of the carboxylic acid-terminated prepolymer and triethylamine in 1,2-dichloroethane, and the reaction was carried out for 5 hours at room temperature to yield a polyester containing a single anhydride unit. The synthesis of polymers containing a variable number of anhydride linkages per chain was carried out in a similar manner using difunctional carboxylic acid-terminated prepolymers as chain-extending segments, and monofunctional carboxylic acid-terminated prepolymers as end-capping units. The difunctional hydroxyl-terminated poly(ϵ-caprolactone) prepolymers were produced using diethylene glycol as the initiator, and then reacted with succinic anhydride to form difunctional carboxylic acid-terminated prepolymers.

Attempted synthesis of multiblock copolymers of butadiene, styrene, and α‐methylstyrene: Effect of polar additives on copolymerizations

AbstractOwing to the low Tg of polystyrene, the mechanical properties of polystyrene‐block‐poly‐butadiene‐block‐polystyrene (SBS) thermoplastic elastomers drop steeply above 60°C. To overcome this behavior, many research groups have considered the replacement of styrene (S) by α‐methylstyrene (MS). We also attempted the synthesis of copolymers with a central polybutadiene (poly B) block and rigid blocks consisting of polystyrene (poly S) and poly(α‐methylstyrene) (poly MS) blocks. Starting from a dilithium initiator, difunctional poly B's with low 1,2 content (10%) were prepared and toluene was added. After addition of a small amount of styrene, MS was added in the presence of a 15% (in vol) of THF at T ≤ −40°C. The copolymers did not have the expected structure and poor mechanical properties resulted, which were, however, still measurable at 120°C. These results probably resulted from secondary reactions involving the MS carbanions. To identify these reactions and to control the polymer structure, the synthesis of multiblock copolymers was carried out with a monofunctional polybutadienyllithium to which were added successively S and MS (in a mixture of hexane and benzene as solvent). MS was added at low temperature in the presence of small amounts of THF or at room temperature after addition of TMEDA. These attempts were unsuccessful, the copolymer being always multimodal as a result of unwanted coupling reactions involving terminal double bonds. The synthesis of elastomers using a coupling reaction of poly MS–poly S–poly B was also considered but the yield in poly B was low since termination reactions involving the polar additive occurred. © 1994 John Wiley &amp; Sons, Inc.

Elastomers based on poly(hexafluoropropylene oxide) crosslinked via triazine groups

AbstractPoly(hexafluoropropylene oxide), poly(HFPO), networks were prepared from functional polymers by end‐linking via triazine groups. The networks were characterised by NMR spectroscopy and by determination of the number of network chains from the shear modulus, and were shown to contain both triazine crosslinks and imidoylamidine links. The mechanical, thermal and chemical properties of the networks were investigated by a range of techniques. A network formed from fully difunctional poly(HFPO) had excellent elastomeric properties above −15°C, and was thermally stable up to 270°C.

Controlled synthesis of α,β‐difunctional poly(hexafluoropropylene oxide)

AbstractAn improved method is described for the preparation of difunctional poly(hexafluoropropylene oxide) of moderate molecular weight (Mn ≈ 6000) in good yield (&gt;80 wt.‐%). With the dependence of chain transfer constant on initiator concentration known, at least under controlled conditions, good molecular‐weight control can be achieved.

Synthesis of new, functionalized poly(butyl vinyl ether) oligomers and novel copolymers containing these materials

AbstractThis paper reports the synthesis and characterization of new, functionalized poly(alkyl vinyl ether) oligomers, and block copolymers containing poly(alkyl vinyl ether) and poly(methyl methacrylate). Using the HI/ZnI2 initiating system in nonpolar solvents (hexane, toluene) at −20°C, both monofunctional and difunctional poly(alkyl vinyl ether) oligomers of predicted molecular weights precisely terminated with aldehyde, primary hydroxyl and ester endgroups have been prepared. Novel diblock copolymers comprised of poly(methyl methacrylate) and poly(butyl vinyl ether) have also been synthesized using a combination of living cationic and living group transfer polymerization.

Preparation of ester terminated poly(alkyl vinyl ether) oligomers and block copolymers using a combination of living cationic and group transfer polymerization

This paper reports the synthesis and characterization of new, functionalized poly(alkyl vinyl ether) oligomers, and block copolymers containing poly(alkyl vinyl ether) and poly(methyl methacrylate). Using the HI/ZnI2 initiating system in nonpolar solvents (hexane, toluene) at -15 °C, both monofunctional and difunctional poly(alkyl vinyl ether) oligomers of predicted molecular weights precisely terminated with ester end groups have been prepared. Novel diblock copolymers comprised of poly(methyl methacrylate) and poly(alkyl vinyl ether) have also been synthesized using a combination of living cationic and living group transfer polymerization (GTP) techniques.

Synthesis of difunctional poly(dimethylsiloxane)s: Application to macromonomer synthesis

AbstractDifunctional poly(dimethylsiloxane) (PDMS) macromonomers were synthesized. Emphasis was put on the synthesis of short PDMS chains exhibiting a narrow molecular weight distribution. This was achieved by the selection of an efficient initiator and under polymerization conditions such as to minimize reshuffling reactions. The macromonomers were subsequently obtained by deactivation of the living sites with an electrophilic unsaturation. Accurate characterization of the macromonomers (GPC, end‐group analysis) was performed.

Computer simulation of end-linked elastomers. I. Trifunctional networks cured in the bulk

The end linking of difunctional poly(dimethylsiloxane) with trifunctional cross linkers in the bulk has been simulated with a computer. A random array of primary chains with a Gaussian end-to-end distribution is generated in an image container on the computer. By joining chain ends at nearby junctions, inter- and intramolecular reactions occur in all species, allowing formation of cyclic structures of any size. At high extents of reaction, the sol components extracted from the spanning forest thus constructed consist of a substantial amount of cycles such as cyclic dimers. The effect of intramolecular reaction increases the extent of reaction by several percent for molecular weights in the range of thousands. Structural statistics of various types of network imperfections and the cycle ranks of the networks are reported. The gels obtained at complete conversions contain loop defects, their populations increasing with lower molecular weights of the prepolymers. The elastic activities of nonstoichiometric systems are compared and discussed.

Poly(vinyl chloride)–polyol (AB)x block copolymers: Synthesis, characterization, and mechanical properties

AbstractPoly(vinyl chloride)–polyol (AB)x block copolymers have been prepared by the condensation polymerization of low‐molecular‐weight hydroxy‐terminated poly(vinyl chlorides) (PVC) and diisocyanate‐capped polyester and polyether diols. The difunctional poly(vinyl chlorides) were synthesized by ozonization of commercial resin followed by metal hydride reduction. The (AB)x block copolymers, which contained 3000 or 4300 molecular weight PVC block sizes and 1000–2000 molecular weight polyol segments, had a wide range of mechanical properties, depending on overall polymer structure. Tensile strengths ranged from 7.8 to 31.5 MPa, elongations from 125% to 610% and torsional stiffness temperatures (Tf) from 25°C to −22°C.