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Poly(bisphenol A carbonate) (PC) is the second most produced engineering polymer in the world; therefore, there are several papers describing its recycling. However, only a few employ a multivariate approach together with a solid statistics basis for proving the trends and capabilities of their methodology. In this work, we report the progress in PC glycolysis, aimed at the production of telechelic hydroxyl-terminated oligomers (PC(OH)2), with controlled molar mass. A Box-Behnken Design (BBD) was employed to evaluate the influence of temperature, ethylene glycol (EG)/PC molar ratio, and polymer solution concentration on the PC(OH)2 molar mass and on reaction yield. The EG/PC molar ratio is the most important factor affecting reaction products. PC(OH)2 yield and bisphenol A residue amounts can be controlled through reaction conditions. BBD allowed the optimization and the scale-up of the reaction, which presented a good correlation between large and small scales. [ABSTRACT FROM AUTHOR]

A statistical-mechanical theory of thermoreversible gelation which is formed by monodisperse telechelic associating polymers with junction multiplicity of three is developed. In the present theory, the effect of loop formation is considered. Using the theory, the properties of the system are obtained, such as the state of association of polymers, the sol-gel transition line, and the number concentration of elastically effective chains. In addition, a Monte Carlo simulation of a bead-spring model of monodisperse telechelic associating polymers is performed. The simulation results are in good agreement with the present theoretical results. Furthermore, the shear modulus is calculated by an application of phantom network theory and compared with the experimental data. The theoretical results agree well with the experimental results. It is shown that the loop formation occurs especially in dilute regime and causes the decrease of the modulus in the regime. [ABSTRACT FROM AUTHOR]

We present a simplified stochastic model designed to exemplify the nonlinear rheology of entangled supramolecular polymeric materials. As a toy model for entanglement effects, we use the Rolie-Poly equations [Likhtman and Graham, J. Non-Newtonian Fluid Mech. 114, 1-12 (2003)] that we decorate with finite extensibility. Additionally, we include a stretch-dependent probability of detachment for the stickers. In both linear and nonlinear regimes, we explore the parameter space, indicating the parameter values for which qualitative changes in response to the applied flow are predicted. Theory and results in the linear rheology regime are consistent with the previous more detailed work of van Ruymbeke and co-workers [van Ruymbeke et al., Macromolecules 43, 4401-4411 (2010)]. Finally, we develop a preaveraged version of the stochastic equations described above to obtain a set of nonstochastic coupled equations that produces very similar predictions but requires less computing resources. This preaveraged model is based on two tensors representing the attached and detached chain populations and a scalar quantity that represents the fraction of these populations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rhodamine-bearing poly(2-isopropyl-2-oxazoline) showed pH- and Al3+-sensitivity. • Polymeric micelle was formed by rhodamine-bearing poly(2-isopropyl-2-oxazoline). • Polymeric micelle was dissociated by Al3+ addition. A telechelic rhodamine-bearing poly(2-isopropyl-2-oxazoline) (Rh-P i PrOx-Rh) was prepared through the living cationic ring-opening polymerization of 2-isopropyl-2-oxazoline and successive end-group functionalization using amine-functionalized rhodamine 6G. Rh-P i PrOx-Rh exhibited hydrophilic–hydrophobic phase transition behavior at a lower critical solution temperature. The rhodamine moieties exhibited pH-responsive and Al3+-sensitive absorption and emission changes. Under physiological conditions, the amphiphilic Rh-P i PrOx-Rh showed the formation of polymeric micelle (critical micellar concentration: 0.042 g/L) that could be dissociated by binding with Al3+. The thermo-responsive properties of Rh-P i PrOx-Rh was also significantly changed by Al3+ addition. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) nanomaterials have long been promised as environment-friendly lubricant additives. However, their agglomeration in base oils have largely limited their practical applications. Here, we report the supramolecular oil gels constructed by amphiphilic telechelic polymers poly(2-hydroxyethyl methacrylate)- block -poly(stearyl methacrylate)- block -poly(2-hydroxyethyl methacrylate) in base oils. 2D nanomaterials GO, h -BN, and g -C 3 N 4 can be homogeneously stabilized in the oil gels over one year, which are the most stable oil dispersions of the 2D nanomaterials reported to date. The oil gels demonstrate excellent lubricating performance, which could be attributed to the 60 − 90 nm thick tribofilms formed on the worn areas. These supramolecular oil gels not only represent an efficient and versatile platform for stabilizing 2D nanomaterials, but also a universal strategy to explore high-performance lubricants. [Display omitted] • Supramolecular oils gels are rationally prepared by amphiphilic telechelic polymers. • 2D nanomaterials can be directly stabilized in the oil gels for more than one year. • The superior dispersion is driven by multiple noncovalent interactions. • All the oil gels demonstrate excellent tribological behavior. • The lubricating mechanism is assigned to the formation of nanothick tribofilms. [ABSTRACT FROM AUTHOR]

RAFT polymerization is attractive for its reliability, facile operation, and high tolerance to a wide variety of monomers, functional groups, solvents, and temperatures. Herein, we report the RAFT-based synthesis of well-defined polymers bearing hydroxyl groups at two terminals by using various monomers. We found that the molecular weight of obtained polymers was half that of a target value when a trithiocarbonate-type chain transfer agent (CTA) was used, suggesting that the polymers unexpectedly cleaved at the middle of the polymer chain as the reaction was proceeding. To address the problem, we synthesized a novel "dithiobenzoate"-type CTA, 2-[N-(2-hydroxyethyl)carbamoyl]prop-2-yl 4-hydroxydithiobenzoate (HECPHD), which bears hydroxyl groups at both terminals, and we succeeded in RAFT polymerization with various monomers without a cleavage of the polymers. [ABSTRACT FROM AUTHOR]

ABSTRACT In this contribution, we reported the synthesis of a series of POSS-terminated polycyclooctadiene (PCOD) telechelics via ring-opening metathesis polymerization (ROMP) approach. Toward this end, 1,4-diPOSS-but-2-ene was synthesized via copper-catalyzed Huisgen cycloaddition reaction (i.e., click chemistry); it was then used as a chain transfer agent (CTA) for the ROMP of cyclooctadiene. The ROMP was carried out with Grubbs second generation catalyst and the POSS-terminated PCOD telechelics with variable lengths of PCOD were obtained by controlling the molar ratios of CTA to cyclooctadiene. All the POSS-terminated PCOD telechelics in bulks were microphase-separated; the morphologies were quite dependent on the lengths of PCOD midchains. The POSS end groups can promote the crystallization of PCOD chains at room temperature, which was in marked contrast to the case of plain PCOD. Compared to the plain PCOD, the POSS-terminated PCOD telechelics displayed improved thermal stability and surface hydrophobicity. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 223-233 [ABSTRACT FROM AUTHOR]

The synthesis of ω-iodo and telechelic diiodo vinylidene fluoride (VDF)-based (co)polymers by iodine transfer polymerization (ITP) of VDF initiated by a trifluoromethyl radical (generated by perfluoro-3-ethyl-2,4-dimethyl-3-pentyl persistent radical, PPFR) is presented. Reactions were carried out in the presence of different chain transfer agents (CTAs, such as trifluoroiodomethane, 1,4-diiodoperfluorobutane, and molecular iodine) with/without tert-butyl 2-trifluoromethacrylate (MAF-TBE). Experimental conditions (nature of the solvents and CTAs, time, temperature, and initial [VDF]0:[CTA]0:[initiator]0 molar ratios) were varied to influence the yield of the reaction (up to 86%), the molar masses (M n), dispersity values (Đ), chain end functionalities, and microstructures of the obtained polymers. Detailed kinetics study enabled to confirm the well-controlled polymerization: (i) synthesis of iodinated polymers with different molar masses (M n,SEC = 1110-5800 g mol-1) and low Đ values (≤1.30), just simply by varying the [VDF]0:[CTA]0 initial molar ratio; (ii) linear increase of M n versus conversion, maintaining low Đ values (≤1.28); (ii) the presence of favored -CH2CF2-I end functionality up to 80% monomer conversion. The compositions and microstructures of all the obtained copolymers were characterized by ¹H and 19F NMR spectroscopies. Deeper mechanistic investigation of the ITP of VDF initiated by •CF3 radical from PPFR was carried out. In the presence of CF3I as the CTA, the competitive presence of CF3 end group in CF3-PVDF-I was evidenced to arise from the CTA and showed a negligible amount of CF3-PVDF oligomer dead chains initiated from •CF3 radical from PPFR. Very low chain defects (due to reversed -CH2CF2-CF2CH2- and -CF2CH2-CH2CF2- in VDF-VDF dyads, even the absence of such a later one) led to high melting points (161-173 °C) of the resulting polymers, as revealed by differential scanning calorimetry. The thermal stability of the polymers increased with higher M n values reaching 270 °C under air, while for copolymers containing MAF-TBE, the degradation occurred from 170 °C attributed to the release of isobutene from the tert-butyl side groups. [ABSTRACT FROM AUTHOR]

Telechelic polycyclooctenes (PCOEs) have been successfully synthesized by ring-opening metathesis polymerization (ROMP)/cross-metathesis (CM) of cyclooctene (COE) using Grubbs' second-generation catalyst (G2) in the presence of epoxide-functionalized chain-transfer agents (CTAs). The monofunctional epoxide oxiran-2-ylmethyl acrylate CTA (1) afforded the isomerized α-(glycidyl alkenoate),ω-propenyl functional (IMF) PCOEs. The use of 1,4-benzoquinone (BZQ) as additive completely inhibited the C C isomerization process, thereby leading selectively to α-(glycidyl alkenoate),ω-vinyl telechelic (MF) PCOE. On the other hand, difunctional epoxide CTAs, bis(oxiran-2-ylmethyl) fumarate (3), bis(oxiran-2-ylmethyl) maleate (4), bis(oxiran-2-ylmethyl) (E)-hex-3-enedioate (5), and (Z)-1,4-bis(oxiran-2-ylmethoxy)but-2-ene (6), selectively afforded the corresponding α,ω-di(glycidyl alkenoate) telechelic PCOEs (DF) along with minor amounts of cyclic nonfunctional (CNF) PCOE. In the presence of these difunctional symmetric CTAs, the mechanism is proposed to proceed through a tandem one-pot CM/ROMP/ring-closing metathesis (RCM) approach. CM was more effective with Z-than E-configurated CTAs (4 > 6 ≫ 3 ≫ 5), regardless of the presence of a methylene group in-between the C C double bond and the glycidyl moiety. Subsequent dithiocarbonatation of the α,ω-diepoxide telechelic PCOEs upon reaction with CS2 in the presence of LiBr quantitatively afforded the first examples of bis(cyclodithiocarbonate) end-functional PCOEs. Ensuing aminolysis of the bis(cyclodithiocarbonate) telechelic PCOEs with the polyether (triethylene glycol) diamine JEFFAMINE EDR-148 quantitatively afforded, at room temperature without any added catalyst, the desired poly(mercaptothiourethane)s NIPUs, as evidenced from FTIR spectroscopy, TGA, and DSC analyses. [ABSTRACT FROM AUTHOR]

A new photoinitiating system for living cationic polymerization of vinyl ethers is reported. In the current approach, visible-light irradiation of dimanganese decacarbonyl (Mn2(CO)10) in the presence of an alkyl bromide results in the formation of carbon-centered radicals. The photochemically generated radicals were then oxidized by diphenyliodonium ions to the corresponding cations. These cations can add vinyl ether monomers, which are then rapidly deactivated by the bromide anions to give α-halide functional end groups. Poly(vinyl ether) chains are then grown through successive photoinduced radical oxidation/addition/deactivation (PROAD) in a controlled manner. The living nature of the system is evaluated through kinetics studies and block copolymer formation. [ABSTRACT FROM AUTHOR]

The synthesis of a novel heterocyclic–telechelic polymer, α,ω-oxetanyl-telechelic poly(3-nitratomethyl-3-methyl oxetane), is described. Infrared spectroscopy (IR), gel permeation chromatography (GPC), and nuclear magnetic resonance (NMR) spectroscopy have been used to confirm the successful synthesis, demonstrating the presence of the telechelic-oxetanyl moieties. Synthesis of the terminal functionalities has been achieved via displacement of nitrato groups, in a manner similar to that employed with other leaving groups such as azido, bromo, and nitro, initiated by nucleophiles. In the present case, displacement occurs on the ends of a nitrato-functionalized polymer driven by the formation of sodium nitrate, which is supported by the polar aprotic solventN,N-dimethyl formamide. The formation of an alkoxide at the polymer chain ends is favored and allows internal back-biting to the nearest carbon bearing the nitrato group, intrinsically in an SN2(i) reaction, leading to α,ω-oxetanyl functionalization. The telechelic-oxetanyl moieties have the potential to be cross-linked by chemical (e.g., acidic) or radiative (e.g., ultraviolet) curing methods without the use of high temperatures, usually below 100°C. This type of material was designed for future use as a contraband simulant, whereby it would form the predominant constituent of elastomeric composites comprising rubbery polymer with small quantities of solids, typically crystals of contraband substances, such as explosives or narcotics. This method also provides an alternative approach to ring closure and synthesis of heterocycles. [ABSTRACT FROM PUBLISHER]

We report supramolecular AB diblock copolymers comprised of well-defined telechelic building blocks. Helical motifs, formed via reversible addition-fragmentation chain-transfer (RAFT) or anionic polymerization, are assembled with coil-forming and sheet-featuring blocks obtained via atom-transfer radical polymerization (ATRP) or ring-opening metathesis polymerization (ROMP). Interpolymer hydrogen bonding or metal-coordination achieves dynamic diblock architectures featuring hybrid topologies of coils, helices, and/or π-stacked sheets that, on a basic level, mimic protein structural motifs in fully synthetic systems. The intrinsic properties of each block (e.g., circular dichroism and fluorescence) remain unaffected in the wake of self-assembly. This strategy to develop complex synthetic polymer scaffolds from functional building blocks is significant in a field striving to produce architectures reminiscent of biosynthesis, yet fully synthetic in nature. This is the first plug-and-play approach to fabricate hybrid π-sheet/helix, π-sheet/coil, and helix/coil architectures via directional self-assembly. [ABSTRACT FROM AUTHOR]

The gas transport properties of graphene oxides (GO) incorporated into highly elastic poly(dimethylsiloxane) (PDMS)/GO elastomers synthesized from graphite and telechelic, amine-terminated PDMS were investigated. To develop broad fundamental understanding of the connection between composite architecture and gas transport properties, both gas barrier and separation characteristics were evaluated. The permeability for several common gases was studied as a function of GO concentration. Incorporating only 3.55 vol% (8 wt%) GO into the PDMS matrix resulted in a more than 99.9% reduction in gas permeation for various gases, such as H 2 , O 2 , N 2 , CH 4 and CO 2 . Moreover, factor of two enhancements in gas selectivities were observed for CO 2 /N 2 and CO 2 /CH 4 compared to neat PDMS membranes. As a supplement to experimental data from scanning-electron and atomic-force microscopy and x-ray diffraction, theoretical models such as the Nielsen and Cussler models were applied to comprehend the dispersion and alignment of GO in the polymer. [ABSTRACT FROM AUTHOR]

Functionalized or multivalent organotellurium chain-transfer agents (CTAs) for living radical polymerization were synthesized by post-modification, which involved the condensation between a carboxylic-acid-functionalized CTA and various amines in excellent yields without affecting the reactive tellurium moiety. The CTAs exhibited high synthetic versatility for radical polymerization and gave structurally well-controlled polymers, such as multiarmed polymers, from various monomers. Because all new CTAs are easily available on a large scale by simple purification, the current method significantly facilitates macromolecular engineering based on organotellurium-mediated radical polymerization (TERP). [ABSTRACT FROM AUTHOR]

We report on the synthesis of heterotelechelic α,ω-dye-labeled polystyrene and poly(methyl methacrylate) via a combination of site-specific atom transfer radical polymerization (ATRP) and click chemistry. By using the advantages of the living polymerization characteristics and a robust coupling efficiency, the Förster/fluorescence resonance energy transfer (FRET) pairs (i.e., carbazolyl and anthryl) were dictated to be at the near-stoichiometric chain ends. The distribution of the end-to-end distance was well described by the energy transfer response of the fluorescent groups between chain ends, which is in reasonable agreement with Gaussian statistics. The synthetic approach described here provides an opportunity to prepare polymeric materials with customized responsive elements and in-depth insight into the statistical scaling dimension of polymers. [ABSTRACT FROM AUTHOR]

A single-step route to telechelic polyethylene (PE) is enabled by selective insertion polymerization. PdII-catalyzed copolymerization of ethylene and 2-vinylfuran (VF) generates α,ω-di-furan telechelic polyethylene. Orthogonally reactive exclusively in-chain anhydride groups are formed by terpolymerization with carbic anhydride. Combined experimental and theoretical DFT studies reveal the key for this direct approach to telechelics to be a match of the comonomers' different electronics and bulk. Identified essential features of the comonomer are that it is an electron-rich olefin that forms an insertion product stabilized by an additional interaction, namely a π-η3 interaction for the case of VF. [ABSTRACT FROM AUTHOR]

We present hybrid molecular dynamics/Monte Carlo simulations of supramolecular networks formed by unentangled telechelic chains with sticky end monomers (or stickers) of finite functionality. The reversible bonding between sticky monomers leads to the formation of sticker clusters with well-defined size distribution, which in turn work as cross-links for transient polymer networks. We study the kinetics of sticky monomer association, the topological structure, and the resulting dynamic and rheological behavior of the supramolecular systems as a function of the sticker bonding energy ε and the parent polymer chain length. Percolated transient networks are formed above a threshold bonding energy around 4.3kBT. At high bonding energies ε ≥ 10kBT, the majority of the stickers are fully reacted and the fraction of open stickers is less than 1%. The conventional picture of a single sticker hopping from one cluster to another is energetically unfavorable. We find the dynamic and rheological behavior of such strongly associated supramolecular networks are dominated by a partner exchange mechanism in which the stickers exchange their associated partners, and so release the imposed topological constraints, through the association and disassociation of sticker clusters. The characteristic time of the partner exchange events grows exponentially with the bonding energy and is up to 2 orders of magnitude longer than the average lifetime of the reversible bonds. As a result, three relaxation regimes can be clearly identified in the stress and chain end-to-end vector relaxation functions as well as the mean-squared displacements of the stickers, which are the initial Rouse regime, the intermediate rubbery regime, and the terminal relaxation regime. A phantom chain hopping model based on the microscopic understanding is proposed to describe the chain relaxation dynamics in the supramolecular networks, which provides numerical predictions in reasonably good agreement with our simulation results. [ABSTRACT FROM AUTHOR]

A series of novel amphiphilic block polyurethanes (PUHE) have been successfully synthesized by solution polymerization of the derived PHB-diol and poly(ethylene glycol) with a coupling agent of 1,6-hexamethylene diisocyanate (HDI), while the PHB-diol was prepared via the transesterification of PHB and ethylene glycol. The hydroxyl contents in PHB-diols range from 1.36 to 1.99 (the molar ratio) as determined by nonaqueous titration. The molecular weight and chemical compositions of PUHE and PHB-diol were investigated by GPC, 1H NMR, and FTIR in detail, which confirm the successful synthesis of PUHE. The tensile strength and elongation at break of PUHE could reach as high as 20 MPa and 210%, as the content of PHB in PUHE is 33%. TGA curves indicate that block-bonding between PHB-diol and PEG increases the thermal stability of PHB-diol. Film degradation of PUHE was studied by weight loss and scanning electron microscope (SEM). It could be concluded that degradation occurred gradually from the surface to the inside and that the degradation rate could be controlled by adjusting the PHB/PEG ratios. These properties make PUHE able to be used as a biodegradable thermoplastic elastomer. [ABSTRACT FROM AUTHOR]

A shape-programmed linearity through supramolecular polymerization is demonstrated by a step-growth double-strand formation of a telechelic oligomeric porphyrin array in which two alternating pyridyl-porphyrin sequenced units are held together by self-complementary ligand-to-metal coordination. The stiff rod-like structure and sufficiently large binding constant of the double-strand unit considerably extended a supramolecular array in the one dimension, which produced a tightly stretched string with a length that exceeded several micrometers. [ABSTRACT FROM AUTHOR]

The effect of telechelic liquid natural rubber (TLNR) compatibilizer on natural rubber (NR) modified by melt-blending with poly(lactic acid) (PLA-NR) is studied using infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and notched Izod impact testing to determine the structural, thermal and mechanical properties. Scanning electron microscopy (SEM) is used to relate these properties to the morphology of the blends and fracture surface of the impact samples. Through this, it is revealed that the addition of LNR significantly improves the tensile and impact strength of PLA-NR, with the greatest compatibilization effect achieved with 6 wt% LNR. This improvement is confirmed through FTIR analysis to be due to a chemical interaction between LNR and PLA that improves the phase morphology of the blend. [ABSTRACT FROM AUTHOR]

A telechelic thermoresponsive polymer, α-amino- ω-thiol-poly( N-isopropylacrylamide) (H2N-PNiPAM-SH), is used as the polymeric glue to assemble gold nanoparticles (AuNPs) around gold nanorods (AuNRs) into a satellite structure. Prepared by reversible addition-fragmentation chain transfer polymerization followed by hydrazinolysis, H2N-PNiPAM-SH is able to interlink the two types of the gold building blocks with the thiol-end grafting on AuNRs and the amine-end coordinating on the AuNP surface. The density of the grafted AuNPs on AuNRs can be tuned by adjusting the molar ratio between AuNPs and AuNRs in the feed. The resulted satellite-like assembly exhibits unique optical property that was responsive to temperature change. [ABSTRACT FROM AUTHOR]

Hydrophobically modified ethoxylated urethanes (HEURs) are an important class of telechelic associative polymers with various industrial applications, in which careful control of the rheology of the solution is required. We report the synthesis of three novel HEUR polymers end-functionalized by dendritic di-substituted benzene alcohol ( HEUR-2Cn , where n is the length of hydrophobic tails) and their rheological properties in aqueous solutions and latex. The concentrated solutions of these HEURs show interesting aggregation and viscoelastic properties dependent of their hydrophobe length: a viscoelastic liquid for HEUR-2C8 , and elastic gels for both HEUR-2C12 and HEUR-2C16 due to their different relaxation behavior. Interestingly, the concentrated solutions of HEUR-2C16 form the strongest transient network with the largest number density of active micellar junctions and slowest relaxation because of its longest hydrophobe. Furthermore, these HEUR polymers have highly efficient thickening performance in latex compared with a conventional HEUR-C16 with −C 16 H 33 end group, because the dendritic two-tail hydrophobes can form more stable absorption on the surface of the latex through bridging between the latex particles than a single hydrophobe. This work opens a new perspective for highly efficient thickeners and also provides new insights into the potential of these HEUR polymers in waterborne coating, cosmetics, dyestuff, medicines and so on. [ABSTRACT FROM AUTHOR]

ABSTRACT We have prepared the amidinium-carboxylate salt bridge-based supramolecular network polymers from a carboxy-terminated telechelic poly( n-butyl acrylate) and a linear polyamidine having N, N′-di-substituted acetamidine group in the main chain. FTIR measurements indicated that the salt bridge was attributed to the three-dimensional network formation. Virtually, no fluidity was observed for the blend containing equimolar amounts of the carboxyl group and the amidine group, which showed a high G′ value of about 1 MPa at −5 °C. For comparison, the supramolecular network polymers crosslinked by ammonium-carboxylate salt were prepared using a linear polyethyleneimine instead of the polyamidine. The blend with equimolar amounts of the carboxyl group and the secondary amino group showed liquid-like fluidity with a G′ value of about 0.01 MPa at −5 °C, which was attributed to the fact that a certain amount of the carboxyl group remained as its free form, as evidenced by FTIR analysis. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2148-2155 [ABSTRACT FROM AUTHOR]

A straightforward synthetic procedure for the double modification and polymer-polymer conjugation of telechelic polymers is performed through amine-thiol-ene conjugation. Thiolactone end-functionalized polymers are prepared via two different methods, through controlled radical polymerization of a thiolactone-containing initiator, or by modification of available end-functionalized polymers. Next, these different linear polymers are treated with a variety of amine/acrylate-combinations in a one-pot procedure, creating a library of tailored end-functionalized polymers. End group conversions are monitored via SEC, NMR, and MALDI-TOF analysis, confirming the quantitative modification after each step. Finally, this strategy is applied for the synthesis of block copolymers via polymer-polymer conjugation and the successful outcome is analyzed via LCxSEC measurements. [ABSTRACT FROM AUTHOR]

This study illustrates that amine functional groups on the ends of telechelic poly(dimethylsiloxane) (PDMS) can undergo post-processing reactions with surface epoxy groups on graphene oxide (GO) to form a robust elastomer during simple heating. In these materials, GO acts both as a nanofiller which reinforces the mechanical properties and participates as a multifunctional crosslinker, thereby promoting elastic properties. Experiments indicate that the telechelic PDMS/GO elastomer is highly crosslinked (e.g., more than 75 wt % is a non-dissolving crosslinked gel) but highly flexible such that it can be stretched up to 300% of its original length. Finally, the PDMS/GO elastomer was tested as a single gas barrier membrane and gas permeability was decreased ∼45% by incorporating 1 wt % (0.43 vol %) of GO, thereby highlighting its potential use in practical applications. [ABSTRACT FROM AUTHOR]

As some complexes of transition metal cations in high oxidation state can oxidize tertiary amines under proper conditions into aminoalkyl radicals to initiate polymerization of electron-deficient vinylic monomers, they form mono-centered redox-initiation pairs for preparation of 100% alpha-amino telechelic polymer. Radical emulsion polymerization of methyl methacrylate (MMA) is performed by using water-soluble amines as a reducing agent and FeIII or CuII as an oxidizing agent. Tertiary amines such as 2-( N, N-dialkylamino)ethanol and N, N, N′, N′-tertramethylethylenediamine exhibit a higher initiation activity. Monomer conversion can reach 80% in 8 h and 95% in 16 h, leading to PMMA with an absolute weight-average molecular weight above 1.5 × 106 g mol−1. The alpha-amino terminal functionality is verified by ultraviolet-induced diarylketone-initiated radical bock polymerization by using these PMMA chains as the macro-sensitizer. Such a facile heterogeneous technique results in syndiotactic-rich high- Tg PMMA (rr > 50%, Tg = 124-127 °C). PMMA chains may be oxidized by FeII-O2 complexes to initiate further radical polymerization, leading to PMMA with a long-chain branched architecture. [ABSTRACT FROM AUTHOR]

Hydroxyl telechelic binders are extensively used in composite solid propellant to impart structural integrity to the solid rocket motor and for functioning as a fuel. Amongst these, hydroxyl terminated polytetramethylene oxide (PTMO) is extensively used for gas generator applications. The hydroxyl groups are cured using isocyanates to polyurethanes. The incompatibility of isocyanates with chlorine free oxidisers like ammonium dinitramide (ADN) and hydrazinium nitroformate (HNF) warrants use of alternate curing methodologies for processing ecofriendly gas generator solid propellants. For this, propargyloxy terminated polytetramethylene oxide (PTMP) was synthesised by the functional modification of PTMO and cured using an azide bearing polymer viz. glycidyl azide polymer (GAP) by ‘Click Chemistry’ approach to form triazole networks. The cure chemistry was studied in detail by differential scanning calorimetry (DSC). The kinetic parameters viz. activation energy was computed to be 106 kJ/mol, pre-exponential factor was 2 × 10 11 s −1 and rate constant at 60 °C was computed to be 4 × 10 −6 s −1 . The cure profile at a given temperature was predicted using the kinetic parameters. Rheological studies revealed that the gel time for curing through the 1, 3-dipolar addition is 220 min against 120 min for curing through the urethane route. The effect of a new alkyne crosslinker on the mechanical properties and efficiency of crosslinking of triazole mediated network was evaluated. The morphological characteristics of the crosslinked network were assessed by scanning electron microscopy (SEM) and Raman spectroscopy. The new binder and cure route provides insensitivity to moisture. The compatibility of the binder with oxidisers ammonium perchlorate (AP) and ADN was evaluated by thermo gravimetric analysis (TGA) according to STANAG 4147 and found to be compatible. Propellants based on PTMP triazole provides superior processability, good mechanical properties and improved ballistic properties in terms of large amount of gas generating species during combustion. [ABSTRACT FROM AUTHOR]

Azido β-cyclodextrins were attached to propiolate-functionalized polydimethylsiloxanes by metal-free click chemistry. The obtained telechelic copolymers spontaneously produced elastomeric gums. Demixing and supramolecular associations are the driving forces for the construction of these strongly associated (but reversible) physical networks. [ABSTRACT FROM AUTHOR]

Terminal-selective transesterification of chlorine-capped poly(methyl methacrylate)s (PMMA-C1) with alcohols was developed as a modular approach to create telechelic and pinpoint-functionalized polymers. Being sterically less hindered and electronically activated, both the α-end ethyl ester and ωend methyl ester of PMMA-C1 were efficiently and selectively transesterified with diverse alcohols in the presence of a titanium alkoxide catalyst, while retaining the pendent esters intact, to almost quantitatively give various chlorine-capped telechelic PMMAs. In sharp contrast to conventional telechelic counterparts, the telechelic polymers obtained herein yet carry a chlorine atom at the ω-terminal to further work as a macroinitiator in living radical polymerization. The iterative process of living radical polymerization and terminal-selective transesterification successfully afforded unique pinpoint-functionalized polymers where a single functional monomer unit was introduced into the desired site of the polymer chains. [ABSTRACT FROM AUTHOR]

By anchoring alkynylplatinum(II) terpyridine molecular tweezer/pyrene recognition motif on the chain-ends of telechelic polycaprolactone, high-molecular-weight supramolecular polymers have been successfully constructed via noncovalent chain extension, which demonstrate fascinating rheological and thermal properties. Moreover, the resulting assemblies exhibit interesting temperature- and solvent-responsive behaviors, which are promising for the development of adaptive functional materials. [ABSTRACT FROM AUTHOR]

This study demonstrates the comprehensive investigation on the reversible linear-cyclic topological conversion of hydrophilic and hydrophobic polymers with various molecular weights. The reactions were triggered by light or heat, which reversibly dimerize and cleave the anthryl or coumarinyl end groups of the telechelics. Poly(ethylene oxide) telechelics with anthryl end groups attached through electron-donating (Ant-O-PEO and Ant-CH2-PEO) and electron-withdrawing (Ant-CO2-PEO) linking groups were synthesized. While Ant-O-PEO and Ant-CH2-PEO decomposed upon photoirradiation at 365 nm, Ant-CO2-PEO efficiently cyclized through the photodimerization of the anthryl end groups both in water and in organic solvents shown by NMR, SEC, and MALDI-TOF MS. The lower the molecular weight, the faster the cyclization proceeded. When cyclized Ant-CO2-PEO was heated at 150 °C in bulk, the polymers quantitatively converted back into the original linear topology. Furthermore, repeatable linear-cyclic topological conversion was confirmed. The reversible topological conversion of hydrophobic poly(tetrahydrofuran) telechelics with anthryl end groups (Ant-PTHF) was also successful. In addition, poly(ethylene oxide) telechelics with coumarinyl end groups (Cou-PEO) were also cyclized by irradiation at 365 nm in water. However, the cyclization hardly occurred when performed in methanol likely due to the lack of sufficient hydrophobic interaction of the coumarinyl end groups. Cyclized Cou-PEO was irradiated at 254 nm to test for linearization, finding the linear product and cyclic precursor were likely photoequilibrated. [ABSTRACT FROM AUTHOR]

The self-assembly in aqueous solution of three novel telechelic conjugates comprising a central hydrophilic polymer and short (trimeric or pentameric) tyrosine end-caps has been investigated. Two of the conjugates have a central poly(oxyethylene) (polyethylene oxide, PEO) central block with different molar masses. The other conjugate has a central poly(l-alanine) (PAla) sequence in a purely amino-acid based conjugate. All three conjugates self-assemble into β-sheet based fibrillar structures, although the fibrillar morphology revealed by cryogenic-TEM is distinct for the three polymers--in particular the Tyr5-PEO6k-Tyr5 forms a population of short straight fibrils in contrast to the more diffuse fibril aggregates observed for Tyr5-PEO2k-Tyr5 and Tyr3-PAla-Tyr3. Hydrogel formation was not observed for these samples (in contrast to prior work on related systems) up to quite high concentrations, showing that it is possible to prepare solutions of peptide-polymer-peptide conjugates with hydrophobic end-caps without conformational constraints associated with hydrogelation. The Tyr5-PEO6k-Tyr5 shows significant PEO crystallization upon drying in contrast to the Tyr5-PEO2k-Tyr5 conjugate. Our findings point to the remarkable ability of short hydrophobic peptide end groups to modulate the self-assembly properties of polymers in solution in model peptide-capped "associative polymers". Retention of fluidity at high conjugate concentration may be valuable in potential future applications of these conjugates as bioresponsive or biocompatible materials, for example exploiting the enzyme-responsiveness of the tyrosine end-groups. [ABSTRACT FROM AUTHOR]

ABSTRACT A new strategy is developed to prepare both α,ω-dithiol and α,ω-divinyl linear telechelic polythiolether oligomers by visible light induced thiol-ene chemistry in the presence of a fac-Ir(ppy)3 photoredox catalyst. Polythiolether oligomers of well-defined end groups and controlled molecular weights have been successfully synthesized at varying monomer molar ratios of 1,4-benzenedimethanethiol (BDMT) to diethylene glycol divinyl ether (DEGVE). 1H NMR and MALDI-TOF MS analyses demonstrate that as-prepared polythiolethers possess high end-group fidelity, which is further supported by the successful polyaddition of polythiolethers bearing α,ω-dithiol and α,ω-divinyl groups. For example, with the α,ω-dithiol- ( Mn = 1900 g mol−1, PDI = 1.25) and α,ω-divinyl-terminated ( Mn = 2000 g mol−1, PDI = 1.29) polythiolethers as macromonomers, the molecular weight of resulting polythiolether is up to 7700 g mol−1 with PDI as 1.67. The reactivity of the terminal thiol group is further confirmed by the addition reaction with N-(1-pyrenyl)maleimide. UV-vis spectra and fluorescene measurements suggest that fac-Ir(ppy)3 undergo a redox quenching process reacted with BDMT to generate thiyl free radicals. With these results, the mechanism of the thiol-ene reaction catalyzed by photoredox catalyst is proposed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 740-749 [ABSTRACT FROM AUTHOR]

Synthesis of telechelic trans-1,4-polyisoprenes (TPI: trans-structure > 95%) was evaluated based on two different methods of oxidative cleavage (indirect cleavage: first epoxidation of TPI, then the selective cleavage of epoxidized units in epoxidized trans-1,4-polyisoprene (ETPI) and direct cleavage of isoprene units in TPI). The influence of solvents and the ratio of oxidative agents was investigated by H-NMR and C-NMR. A series of well-defined telechelic TPI with double terminated functional groups and less side reaction (molecular weight distribution range: 1.96?2.26) were synthesized by indirect cleavage in chloroform. Telechelic TPI showed similar crystallization behavior with TPI and interesting cold crystallization behavior characterized by DSC. [ABSTRACT FROM AUTHOR]

Telechelic and 3-arm star-shaped poly(l-lactic acid)s (PLLAs) and poly(d-lactic acid)s (PDLAs) end-functionalized by 2-ureido-4[1H]-pyrimidione (UPy) self-complementary quadruple hydrogen-bonding motifs were synthesized by terminally modifying the corresponding hydroxyl-terminated polymers. The PLLA/PDLA stereoblock supramolecular polymers (sb-SMPs) with linear and branched architectures were further prepared by mixing the UPy end-functionalized telechelic, 3-arm star-shaped PLLA and PDLA through the dimerization of UPy groups, as verified by viscometry. Crystallization kinetics, polymorphic crystalline structure, and lamellae morphology of the PLLA/PDLA sb-SMPs were investigated and compared with the corresponding blends without UPy end functionalities. Compared to the PLLA/PDLA blends, the sb-SMPs exhibit higher crystallization rate and prefer to crystallizing into the high-melting-point stereocomplex (sc), rather than the low-melting-point homocrystallite in both the nonisothermal and isothermal crystallization processes. The sc crystallization ability and crystallization rate of sb-SMPs are further enhanced with increasing the concentration of terminal UPy groups or decreasing the block lengths of PLLA and PDLA. The enhanced sc crystallization ability and faster crystallization rate of sb-SMPs are ascribed to the hydrogen bonding interactions formed between the terminal UPy groups of PLLA and PDLA. Due to the preferential sc crystallization, the sb-SMPs exhibit smaller long periods than the corresponding PLLA/PDLA blends. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of valuable telechelic phosphonated rubber from polydienes. • Controlled depolymerization process thanks to the ruthenium-cross-metathesis reaction. • Synthesis of valuable telechelic phosphonated polydienes from ground light vehicle tire waste powder. A controlled degradation process enabling polydiene depolymerization and using the olefin metathesis reaction with a phosphonated allylic chain transfer agent (CTA) is reported. This process afforded the functionalization of elastomers by phosphonate groups to lead to phosphonated telechelic polymers with a quite low dispersity. The metathetic degradation reaction proceeded successfully on waste tires to provide phosphonated telechelic polymers that can be used as secondary raw materials for various applications. This strategy is a logical solution to develop a circular economy approach concerning the recycling of the waste tires. [ABSTRACT FROM AUTHOR]

This work describes a versatile and efficient condensation polymerization route to aliphatic polyesters by organo-catalyzed (4-dimethylaminopyridine) transesterification reactions between an activated pentafluorophenyl-diester of adipic acid and structurally different diols. By introducing "monofunctional impurity" or "stoichiometric imbalance," this methodology can afford well-defined end-functionalized polyesters with predictable molecular weights and narrow dispersity under mild conditions without any necessity for the removal of the byproducts to accelerate the polymerization reaction, which remains a major challenge in conventional polyester synthesis with non-activated diesters. Wide substrate scope with structurally different monomers and the synthesis of block copolymers by chain extension following either ring-opening polymerization or controlled radical polymerization have been successfully demonstrated. Some of the polyesters synthesized by this newly introduced approach show high thermal stability, crystallinity, and enzymatic degradation in aqueous environments., (© 2022 Wiley-VCH GmbH.)

The synthesis of hydrophilic, thermoresponsive, and zwitterionic polymethacrylates is reported by Cu(0)-mediated reversible deactivation radical polymerization in water and/or water/alcohol mixtures. The predisproportionation of [CuI(PMDETA)Cl] in water prior to initiator and monomer addition is exploited to yield well-defined polymethacrylates with full monomer conversions in 30 min. The addition of supplementary halide salts (NaCl) enables the synthesis of various molecular weight poly[poly(ethylene glycol) methyl ether methacrylate] (PEGMA475) ( DPn = 10-80, Mn ≈ 10 000-40 000 g mol−1) with full monomer conversion and narrow molecular weight distributions attained in all cases ( Đ ≈ 1.20-1.30). A bifunctional PEG initiator (average Mn ≈ 1000 g mol−1) is utilized for the polymerization of a wide range of methacrylates including 2-dimethylaminoethyl methacrylate, 2-morpholinoethyl methacrylate, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, and 2-methacryloyloxyethyl phosphorylcholine. Despite the high water content, high end group fidelity is demonstrated by in situ chain extensions and block copolymerizations with PEGMA475 yielding well-defined functional telechelic pentablock copolymers within 2.5 h. [ABSTRACT FROM AUTHOR]

Disulfonated poly(arylene ether sulfone) copolymer membranes are of interest for water purification by desalination. These negatively charged copolymers exhibit lower fouling and greatly improved resistance to oxidants such as chlorinated disinfectants compared to state-of-the-art highly cross-linked aromatic polyamide, porous polysulfone supported thin film composite (TFC) systems. A systematic series of controlled molecular weight 4,4'-biphenol and bisphenol A based partially disulfonated poly(arylene ether sulfone)s were synthesized with terminal amine functionalities via end-capping with m-aminophenol. The stoichiometric balance of the end-capping reagent, bisphenols, and two activated dihalides controlled Mn and degree of disulfonation. Oligomers with controlled molecular weights and ionic content were thermally cross-linked with a multifunctional epoxy resin (TGBAM) derived from methylene dianiline. The residual masses from boiling solvent extraction confirmed high gel fractions. The networks had improved salt rejection compared to linear controls due to reduced swelling, and this proved to be a valuable parameter for enhancing transport properties. The cross-linked highly sulfonated copolymers produced the best water purification properties to date observed for disulfonated polysulfone membranes by retaining high salt rejection with enhanced water permeabilities. For example, an epoxy-cross-linked 4,4'-biphenol-based 60% disulfonated polysulfone with an ion exchange capacity (IEC) of 1.85 mequiv/g had a salt rejection of 96.7% and a relatively high hydraulic water permeability of 1.18 (L μm m-2 h-1 bar-1), compared to a linear 4,4'-biphenol-based 40% disulfonated polysulfone with a similar ionic content (IEC = 1.78) that only had a salt rejection of 92.5% and a hydraulic water permeability of 0.62 (L μm m-2 h-1 bar-1). [ABSTRACT FROM AUTHOR]

In this study, thermo-responsive poly( N -isopropyl acrylamide)- g -gold nanorods (PNIPAAm- g -GNRs) were prepared by grafting telechelic PNIPAAm-SH to the GNRs. They were stable in aqueous medium where the GNRs were protected by PNIPAAm chains as revealed by transmission electron microscope. The longitudinal surface plasmon absorbance had a red shift to 810 nm, and the lower critical solution temperature (LCST) of the PNIPAAm was increased to 34.9 °C. After being irradiated by near-IR for 5 min, the PNIPAAm- g -GNRs solution indicated a temperature increment above its LCST. The opto-thermal effect thus could induce the morphology change of the PNIPAAm, which was found to be reversible. Furthermore, the PNIPAAm- g -GNRs had a much lower cytotoxicity than the surfactant-stabilized GNRs. The cell viability of fibroblast after two days of culture could still reach 89.0% relative to the control. Therefore, the PNIPAAm- g -GNRs could be used as drug carriers in which the drug-release could be controlled by remote near-IR. [ABSTRACT FROM AUTHOR]

A simple, one-pot approach to synthesize random semicrystalline/amorphous multiblock copolymers (12–17 blocks per chain on average) is demonstrated that takes advantage of acyclic diene metathesis (ADMET) polymerization of α,̉-divinyl-terminated telechelic polyolefins. This synthetic approach offers a generic, viable and economical route to polyolefin-based multiblock copolymers and may be extendable to broader families of multiblock materials. [ABSTRACT FROM AUTHOR]

Polyepoxyurethane polymers were synthesized from PolyHydroxyUrethane (PHU) prepolymers terminated amine and epoxy multifunctional. In order to ensure this, PHU prepolymers was synthesized from the reaction between α, ω-bis-cyclic-carbonates (poly(propylene)oxide bis-carbonates) and different excess of diamines (ethylenediamine) to terminate these prepolymers by amine with differents chain length. Then, these aminotelechelic PHU oligomers were re-used in formulation with multifunctional epoxy compound (Bisphenol A Diglycidyl Ether, Di-epoxydized Cardanol or Phloroglucinol Tris Epoxy) to synthesize polyepoxyurethane polymers called also hybrid polymers. Firstly, the raw materials were analyzed in order to determine proportion stoichiometry for carbonate/amine and of hybrid materials formulations. Secondly, for the purpose to demonstrate that the reaction carbonate/amine form hydroxyurethane compound, a model study was realized. Then, syntheses and analyzes of prepolymers terminated amine by 1 H, 13 C NMR, TGA and DSC was conducted. Once these oligomers analyzed, the hybrid polymers were formulated from epoxy compounds at different temperatures to determine the best cross-linking proceed. Epoxyurethane polymers were characterized by ATG, DSC and measurement of their swelling index and gel content. These materials exhibited glass transition temperature between −5 °C and 42 °C and a thermal stability above 320 °C at 30% of weight loss. [ABSTRACT FROM AUTHOR]

New poly(urethane urea)s based on telechelic poly(methyl acrylate)s (PMAs) and different diisocyanates and diamines are prepared by a two-step polyaddition process--formation of an isocyanate telechelic prepolymer followed by chain extension with a diamine to form the final poly(urethane urea)s. Hydroxyl-telechelic or mixed amino-hydroxyl-telechelic PMAs are obtained by two different concepts: (i) according to the first concept methyl acrylate (MA) was polymerized by single electron transfer-living radical polymerization (SET-LRP) using 2-hydroxyethyl 2-bromoisobutyrate as initiator followed by nucleophilic substitution of the halogen end group with n-butylamine, 2-methylamino ethanol, or 3-amino-1-propanol and (ii) according to the second concept after SET-LRP under the same conditions the halogen end group is converted to an azide followed by a click reaction using sodium azide and propargyl alcohol in a one-pot reaction. Applying the second concept, a hydroxyl-functional PMA with a share of 83 mol% bifunctionality is obtained. This PMA-diol is used in polyaddition reaction with different diisocyanates (isophorone diisocyanate (IPDI), 4,4'-methylenebis(cyclohexyl isocyanate) (HMDI), and 4,4 -methylenediphenyl diisocyanate (MDI)) resulting in an isocyanate-telechelic prepolymer followed by chain extension with the corresponding diamines (isophorone diamine (IPDA), 4,4'-methylenebis(cyclohexyl amine) (HMDA), and 4,4'-methylenediphenyl diamine (MDA)). A The polyurethane based on hydroxyl-telechelic PMAs and IPDI/IPDA has a molecular weight of Mn = 44 500 g mol-1 and a dispersity Ð = 3.5, respectively; those based on HMDI/HMDA and MDI/MDA have Mn = 24 600 g mol-1 and Ð = 2.2 and Mn = 16 100 g mol-1 and Ð = 2.0, respectively. [ABSTRACT FROM AUTHOR]

Isoconversional analysis was applied to non-isothermal bulk cure kinetics of uncatalyzed polyurethane (PU) resins based on telechelic hydoxyl natural rubber (HTNR) and poly[(phenyl isocyanate)-co-formaldehyde] (P-MDI). The dependency of apparent activation energy on conversion led to the identification of two different kinetic models, each involving two activation energies: a phenomenological model based on the Kamal–Sourour equation with non integer reaction exponents; and a new semi-mechanistic model assuming a main second order reaction between alcohols and isocyanates forming urethane linkages and a secondary reversible reaction forming allophanates that is known to become significant above 120 °C. Such a model based on mechanistic considerations allowed us to explain the variations of reactivity of the HTNR polyols with its average molecular weight. [ABSTRACT FROM AUTHOR]

Well-defined α-(cyclic carbonate), ω-hydroxyl asymmetric telechelic poly(ε-caprolactone)s (PCLs) were prepared with good end-group fidelity by ring-opening polymerization (ROP) of ε-CL catalyzed by Sn(Oct) in conjunction with a renewable, functional bio-based initiator namely glycerol 1,2-carbonate (GC) in bulk at 110 °C. The end group's structure derived from the alcohol initiator was confirmed by NMR, FTIR and MALDI TOF MS. The living character of ROP of ε-CL using GC/Sn(Oct) was demonstrated by the linear correlation of molecular weight versus monomer conversion. End-capping reaction of α-(cyclic carbonate), ω-hydroxyl asymmetric telechelic PCL with itaconic anhydride to yield α-(cyclic carbonate), ω-(itaconic acid) asymmetric telechelic PCL was presented. Five-membered cyclic carbonate end group reaction with 2-phenylethylamine enabled the hydroxyurethane end functional PCL without the use of the relatively more hazardous isocyanates and without any by-product. [ABSTRACT FROM AUTHOR]

We used statistical mechanics to design polymers that defy conventional wisdom by self-assembling into "megasupramolecules" (≥5000 kg/mol) at low concentration (≤0.3 weight percent).Theoretical treatment of the distribution of individual subunits--end-functional polymers--among cyclic and linear supramolecules (ring-chain equilibrium) predicts that megasupramolecules can format low total polymer concentration if, and only if, the backbones are long (>400 kg/mol) and end-association strength is optimal. Viscometry and scattering measurements of long telechelic polymers having polycyclooctadiene backbones and acid or amine end groups verify the formation of megasupramolecules. They control misting and reduce drag in the same manner as ultralong covalent polymers. With individual building blocks short enough to avoid hydrodynamic chain scission (weight-average molecular weights of 400 to 1000 kg/mol) and reversible linkages that protect covalent bonds, these megasupramolecules overcome the obstacles of shear degradation and engine incompatibility. [ABSTRACT FROM AUTHOR]

In this study a degradation process of flexible polymer networks fabricated from telechelic macromonomers comprising methacrylic functionalities and dimer fatty acid derivatives were discussed. Hydrolytic degradation in simulated body fluid (SBF) as well as enzymatic degradation with a lipase of six different systems comprising ester, anhydride and urethane bonds was investigated. In parallel, in order to make a comparison with other analogous polymeric systems, reference materials were also considered. The degradation process was monitored by determining the weight loss and water uptake, FT-IR analysis and changes in pH of degradation medium as a function of time. A rapid progress of degradation of the network containing anhydride bonds was observed. Furthermore, polymer networks showed low water absorption from 10 to 2 wt.%. Polymer networks did not release acidic degradation products in an amount that causes acidification of the medium except the anhydride network. The IR analysis of characteristic bands showed degradation of specific bonds leading to formation of possible hydrolysis products of these networks such as poly(methacrylic acid), macromonomer precursor molecules and derivatives of the macromonomers having terminal carboxylic and hydroxyl groups. We demonstrated that the referred polymeric networks undergo a controlled gradual degradation in the presence of lipase. This study provides an example of how the susceptibility of cross-linked polymers to degradation can be tailored by varying their molecular structure, depending on the needs. [ABSTRACT FROM AUTHOR]

ABSTRACT A series of epoxy-functional telechelic oligomers containing oxetane end groups have been synthesized. The precursor monomer, extracted from outer Birch bark, was first polymerized through enzyme-catalyzed esterification to form oligomers having epoxy and/or oxetane groups in the structures. The oligoesters were subsequently crosslinked through cationic polymerization either by epoxy or oxetane homopolymerization or copolymerization when both functionalities were present. A study of the polymerizations of the resins was performed ' in situ' using real-time Fourier transform infrared spectroscopy revealing a preferred copolymerization when compared with the homopolymerization. By tailoring the different structures, it was possible to control the final mechanical properties of the networks. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2258-2266 [ABSTRACT FROM AUTHOR]

Poly(l-lactide) (PLA), a biodegradable and biorenewablepolymer, has many excellent properties that are equivalent to thoseof petroleum-derived plastics such as polystyrene, aromatic polyesters,etc. However, a major disadvantage of PLA which limits its processabilityis its poor melt elasticity. In this work we explore the possibilityof improving the viscoelastic properties of PLA melt by incorporatingionic groups on the polymer. Specifically, we demonstrate the synthesisof star telechelic PLA anionomers by a three-step procedure involvingsynthesis of Star PLA, converting the hydroxyl end groups into carboxylicacid end groups, and finally converting these into ionic groups. Rheologydata showed a dramatic increase in the elasticity of the star telechelicionomer melts relative to the Star PLA melts. The viscoelasticityof star telechelic ionomers melts could be modulated by varying thenumber of ionic groups per molecule. [ABSTRACT FROM AUTHOR]