Polyester nanoparticles by non‐aqueous emulsion polycondensation

A versatile non‐aqueous emulsion polycondensation process for the mild fabrication of polyester nanoparticles is presented. Spherical nanoparticles with diameters smaller than 60 nm are prepared in non‐aqueous emulsion systems. These emulsions consisted in one case of DMF dispersed in n‐hexane and in a second with acetonitrile dispersed in a continuous cyclohexane phase. Stabilization of these systems was achieved by using a polyisoprene‐polymethylmethacrylate block copolymer. The suitability of these aprotic emulsions for synthesizing polyester nanoparticles by emulsion polycondensation having molecular weights up to 22,000 g/mol is demonstrated. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1101–1108, 2007     

New synthetic method for aromatic polyketones from bis(arylsilane)s and aromatic dicarboxylic acid chlorides

A new synthetic method for aromatic polyketones was developed through Friedel–Crafts polycondensation of bis(arylsilane) monomers with aromatic dicarboxylic acid chlorides. The solution polycondensation of these monomer pairs in the presence of aluminum chloride in 1,2‐dichloroethane readily afforded aromatic polyketones having inherent viscosities up to 0.37 dL/g with the elimination of chlorotrimethylsilane. The polycondensation proceeded through aromatic electrophilic ipso substitution, the mechanism of which is very similar to that of normal Friedel–Crafts acylation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2729–2735, 2002     

Direct dehydration polycondensation of lactic acid catalyzed by water‐stable Lewis acids

Poly(L ‐lactic acid) (PLLA) is generally produced by ring‐opening polymerization of (S,S)‐lactide, which is prepared from dehydration polycondensation of lactic acid and successive depolymerization. Results of this study show that scandium trifluoromethanesulfonate [Sc(OTf)₃] and scandium trifluoromethanesulfonimide [Sc(NTf₂)₃] are effective for one‐step dehydration polycondensation of L ‐lactic acid. Bulk polycondensation of L ‐lactic acid was carried out at 130–170 °C to give PLLA with M_n of 5.1 × 10⁴ to 7.3 × 10⁴ (yield 32–60%). The solution polycondensation was performed at 135 °C for 48 h to afford PLLA with M_n of 1.1 × 10⁴ with good yield (90%). In no case did ¹H NMR, specific optical rotation, or DSC measurement confirm racemizations. The catalyst was recovered easily by extraction with water and reused for polycondensation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5247–5253, 2006     

Synthesis and characterization of novel biodegradable aliphatic poly(ester amide)s containing cyclohexane units

Polyesters provide a good basis to work on for designing novel biodegradable materials that are also mechanically and thermally resistant. In this study, a series of aliphatic poly(ester amide)s (PEA) based on cyclohexane units was synthesized. Block‐copolymers of cyclohexyl sebacate and cyclohexyl sebacamide were produced by controlling the length of the ester block and the amount of amide during a two‐step melt/interfacial polycondensation reaction. Films produced from these materials could retain their shape above 373 K due to the physical network of amide hydrogen‐bonding. Thermal properties were also evaluated, with various melting and softening points obtained depending on the PEA composition. The determining factor for mechanical properties was the amount of amide introduced, with films containing up to 10 mol % amide showing the best handleability and flexibility. Tensile properties typical of an amorphous viscoelastic material were observed, but with much superior elongation to break achievable (～1700%). These materials were also shown to be hydrolyzable, noncytotoxic, and favorable for cell attachment: they may therefore have a promising future in the area of medical devices or packaging, especially as their properties can be tuned by changing their composition. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1785–1795, 2006     

s‐Triazine‐based hyperbranched polyethers: Synthesis,characterization, and properties

A series of s‐triazine‐based hyperbranched polyethers (HBPE) have been synthesized to obtain thermostability but flexible polymers by an interfacial polycondensation of different diols as A₂ and cyanuric chloride as B₃ monomers using A₂ + B₃ approach in the presence of a phase transfer catalyst. The polymerization reaction parameters are optimized, and the results indicate that the optimum conditions for the interfacial polycondensation are a 2:3 mole ratio of cyanuric chloride to diol using butanediol, benzyldimethylhexadecyl ammonium chloride as the catalyst, dichloromethane as the organic solvent, and a three‐step procedure with keeping the reaction mixture at different low temperatures for 2h/2h/5h. Other techniques such as high‐temperature solution, one‐step polycondensation, and transesterification were also carried out to synthesize the HBPE but proved to be not suitable due to large number of side reactions. The synthesized polymers were characterized by FTIR, ¹H NMR, and ¹³C NMR spectroscopy, hydroxyl number determination, solution viscosity measurements, and GPC analysis. The thermal behavior of the hyperbranched polymer was investigated by thermogravimetric analysis and differential scanning calorimetry. All the results were compared with those from an analogous linear polyether, obtained from 2‐methoxy‐4,6‐dichloro‐s‐triazine and butanediol by using the same polymerization technique. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3994–4004, 2010     

Functionalization of nanoparticles for dispersion in polymers and assembly in fluids

The fluorescent, magnetic, and conductive properties of nanoparticles can transform polymer-based materials into composites with higher levels of sophistication than found in polymers alone. The ligand chemistry of nanoparticles is critically important in the development of polymer–nanoparticle composites to prevent nanoparticle aggregation and direct their assembly within polymers. Nanoparticle ligands can also prevent aggregation in solution and direct the assembly of nanoparticles at fluid–fluid interfaces, where interfacial chemistries can be performed to provide new routes to ultrathin composite sheets and capsules. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5076–5086, 2006     

Synthesis and characterization of new polyamides based on Diphenylaminoisosorbide

New aromatic polyamides were synthesized by the microwave‐assisted polycondensation of an optically active isosorbide‐derived diamine with different diacyl chlorides in the presence of a small amount of N‐methylpyrrolidinone. Polymers with inherent viscosities between 0.22 and 0.73 dL/g were obtained corresponding to molecular weights up to 140,000 g/mol. With interfacial polymerization or the Higashi method, lower molecular weight polymers were obtained with inherent viscosities in the range of 0.04–0.36 dL/g. Differential scanning calorimetry measurements clearly demonstrated the high thermal stability of these polymers (mp = 180–300 °C) and the absence of decomposition. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6480–6491, 2005     

Preparation of polyamides derived from 1,6-diamantane dicarboxylic chloride by solution polycondensation and interfacial polycondensation

1,6-Diamantane dicarboxvlic acyl chloride ( I ) was used as a monomer with various aromatic diamines to synthesize polyamides by interfacial polycondensation and solution polycon-densation. The polyamides prepared by interfacial polycondensation had inherent viscosities between 0.38 and 0.15 dL/g. The polyamides prepared by solution polycondensation had inherent viscosities between 0.62 and 0.25 dL/g. The polyamides IIIa prepared by solution polycondensation showed the main melting transition at 380°C by dynamic mechanical analysis. In addition, it was quite temperature-stable and maintained good mechanical properties (G′?10⁸ Pa) up to high temperatures close to the main transition well above 350°C. The polyamide IIIA had a tensile strength of 35 MPa, elongations to break of 10%, and initial modulus of 0.8 GPa. Some of the polyamides were soluble in NMP, DMAc, and DMSO, depending on soft segment moiety of diamine ( II ). The polyamides prepared by interfacial polycondensation have a greater tendency to form crystal than those prepared by solution polycondensation, as evidenced by x-ray diffraction studies. These polyamides had glass transition temperatures in the 270–300°C range, and 5% weight loss temperatures up to 435°C in nitrogen. © 1995 John Wiley & Sons, Inc.     

Synthesis of furan dimer‐based polyamides with a high melting point

Polyamide composed of furan dimer, which is prepared from biomass‐derived organic molecule 2‐furfural, is synthesized. The reaction of 2,2′‐furan dimer 5,5′‐dicarbonyl chloride with several 1,ω‐diamines was carried out with a solution or interfacial polycondensation leading to the corresponding polyamide. Measurement of the melting point was performed resulting to exhibit a higher temperature compared with the related polyamide bearing a single furan ring composed of furan‐2,5‐dicarboxylic acid (FDCA). Thermal analyses (TG–DTA) also indicated higher temperatures of decomposition than those of FDCA‐derived polyamide. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1516–1519     

New regioselective synthesis of metalinked aromatic polyketones from metasubstituted bis(arylsilane)s and aromatic dicarboxylic acid chlorides

A new regioselective synthesis of metalinked aromatic polyketones was achieved for the first time. New metaconnected aromatic polyketones with inherent viscosities of up to 0.49 dL/g were regioselectively synthesized by the solution polycondensation of metasubstituted bis(arylsilane)s with aromatic dicarboxylic acid chlorides in the presence of aluminum chloride in 1,2‐dichloroethane along with the elimination of chlorotrimethylsilane. The polycondensation proceeded through aromatic electrophilic ipso‐substitution. The metalinked aromatic polyketones had considerably lower glass‐transition temperatures and 10% weight‐loss temperatures than those of their counterpart paracatenated aromatic polyketones. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1428–1434, 2003     

Polycondensation of α‐amino acid esters in the presence of yttrium triflate as a Lewis acid

To develop polycondensation methods for poly(α‐amino acid)s, we describe a first examination to use yttrium triflate as a Lewis acid for polycondensation of α‐amino acid esters. In the absence of Lewis acid, no polycondensation of 2‐methoxyphenyl glycinate ( 1b ) at room temperature proceeded. While the polycondensation of 1b was carried out with 5 mol % yttrium triflate, a condensation product of glycine was obtained in 16% yield. Although polycondensation of 4‐nitrophenyl L ‐leucinate ( 1c ) and 4‐nitrophenyl L ‐valinate ( 1d ) were also promoted with 5 mol % yttrium triflate, the condensation products of both α‐amino acid esters were obtained in only a few percent yield. When 1d was polymerized in the presence of 100 mol % yttrium triflate, high molecular weight poly(L ‐valine) was obtained in 91% yield. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4731–4735, 2006     

An infiltration method for preparing single‐wall nanotube/epoxy composites with improved thermal conductivity

Recent studies of SWNT/polymer nanocomposites identify the large interfacial thermal resistance at nanotube/nanotube junctions as a primary cause for the only modest increases in thermal conductivity relative to the polymer matrix. To reduce this interfacial thermal resistance, we prepared a freestanding nanotube framework by removing the polymer matrix from a 1 wt % SWNT/PMMA composite by nitrogen gasification and then infiltrated it with epoxy resin and cured. The SWNT/epoxy composite made by this infiltration method has a micron‐scale, bicontinuous morphology and much improved thermal conductivity (220% relative to epoxy) due to the more effective heat transfer within the nanotube‐rich phase. By applying a linear mixing rule to the bicontinuous composite, we conclude that even at high loadings the nanotube framework more effectively transports phonons than well‐dispersed SWNT bundles. Contrary to the widely accepted approaches, these findings suggest that better thermal and electrical conductivities can be accomplished via heterogeneous distributions of SWNT in polymer matrices. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1513–1519, 2006     

Enlarging the library of poly‐(L‐lysine citramide) polyelectrolytic drug carriers

Poly‐(L ‐lysine citramide) is a degradable drug carrier of the polyelectrolyte type that is composed of citric acid and L ‐lysine building blocks. In a previous work, poly‐(L ‐lysine citramide) was synthesized by the interfacial polycondensation of α‐hydroxy acid protected citryl dichloride with COOH‐protected lysine diamine. Because of head‐to‐head and head‐to‐tail and tail‐to‐tail linkages in the chains as well as various side reactions such as deprotection of the α‐hydroxy acid moieties and intramolecular imide ring formation, a very large family of degradable polyelectrolyte copolymers was obtained. All the members of this family hydrolytically degrade to the same end products. In this study, another route was explored based on the polycondensation of α‐hydroxy acid protected citric acid pentafluorophenyl diesters, namely, citrobenzal dipentafluorophenyl and citrochloral dipentafluorophenyl with N‐N′‐trimethylsilylated COOH‐protected L ‐lysine. The resulting polymers were characterized by IR, NMR, and size exclusion chromatographic analyses. The resulting chain structures and repeat units were identified from these characterizations and are discussed as compared with characteristics exhibited by analogous polymers resulting from interfacial polycondensation. Differences observed at the intermediate stage involving protected polymers were largely erased during the final deprotection stage because of imide formation during final hydrolysis under the selected conditions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3475–3484, 2001     

Stimuli‐responsive polymers. VIII. Polyesters and poly(ester amides) containing azobenzene and chiral binaphthylene segments: Highly adaptive materials endowed with light‐, heat‐, and solvent‐regulated optical rotatory power

Azobenzene‐modified polyesters and poly(ester amide)s fitted with chiral, atropisomeric binaphthylene segments were prepared by a series of low‐temperature polycondensation reactions carried out in polar solvent media. When compared with their polyaramide counterparts studied earlier, these materials had significantly improved solubility behaviors and were readily dissolved by a wide range of organic solvents. In solution, each of these constructs underwent photoinduced oscillations in optical rotatory power when subjected to multiple UV‐light/visible‐light illumination cycles that drove trans?cis isomerization reactions along their polymer chains. Light‐regulated chiroptical perturbations were dependent on polymer backbone structures and were further modulated by well‐coordinated temperature fluctuations and by the nature of the solvent medium employed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 207–218, 2006     

A convenient room temperature polycondensation toward hyperbranched AB2‐type all‐aromatic polyesters with phenol terminal groups

As a convenient alternative to the classical melt polycondensation the one‐pot solution polycondensation of suitable AB₂ monomers under mild conditions has been successfully adapted to hyperbranched all‐aromatic polyester with phenol terminal groups. The polymerization was performed in solution at room temperature directly using commercially available 3,5‐dihydroxybenzoic acid as monomer and 4‐(dimethylamino) pyridinium 4‐tosylate as catalyst to suppress the formation of N‐acylurea. Different carbodiimides as coupling agents were investigated to find the optimal esterification conditions. The polymers have been characterized extensively and were compared with their well‐known analogs synthesized in melt. The characterization was carried out by NMR spectroscopy, size exclusion chromatography, and asymmetric flow‐field flow fractionation as an alternative separation technique for multifunctional polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5158–5168, 2009     

Friction and nanowear of polystyrene against hydrophobic and hydrophilic substrates

The ambition of this study is to analyze the role of interfacial interactions in friction and nanowear of polystyrene, by comparing friction against hydrophobic wafers (methyl‐terminated) and hydrophilic wafers (hydroxyl‐terminated) as a function of sliding velocity and normal force. Friction experiments are performed with a translation tribometer and nanowear investigation is achieved by using atomic force microscopy (AFM) analysis of the wafer surfaces after friction. Experimental results show that the friction coefficients measured on hydrophilic surfaces are always larger than those obtained with hydrophobic surfaces, indicating a relationship between friction and interfacial interactions. Elsewhere, AFM analysis shows that polystyrene transfer appears for a higher normal force in the case of hydrophobic substrates compared to hydrophilic one. However, the corresponding tangential (or friction) force necessary to detect transfer is quite similar for both types of substrates, indicating that the initial wear of polystyrene occurs for a similar threshold interfacial shear. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2449–2454, 2006     

Poly(ortho‐phenylene ethynylene)s: Synthetic accessibility and optical properties

Poly(ortho‐phenylene ethynylene)s (PoPEs) have been synthesized via an in situ activation/coupling AB′ polycondensation protocol. The resulting polymers have been characterized by several analytical methods and are shown to have no structural defects. Although the Sonogashira–Hagihara polycondensation reaction is less efficient than for the preparation of the corresponding meta‐ and para‐linked polymers, presumably because of steric hindrance caused by the ortho substituents, the process can be accelerated by the use of microwave irradiation. Optical spectroscopy indicates solvent‐dependent conformational changes between extended transoid and helical cisoid conformations, providing the first experimental evidence for solvophobically driven folding of the PoPE backbone. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1619–1627, 2006     

Preparation and properties of ordered and random polyamide-esters from 4-(4-amino-α,α-dimethylbenzyl)phenol and aromatic diacyl chlorides

Random polyamide-esters were prepared directly by the interfacial and solution polycondensation of 4-(4-amino-α,α-dimethylbenzyl)phenol (I) with iso- and terephthaloyl chlorides. Authentic samples of ordered polyamide–esters with an amide-amide–ester-ester structure were synthesized by the two-step procedure; that is, the preparation of amide–bisphenol monomers from I and subsequent polycondensation with aromatic diacyl chlorides. The random and ordered polyamide–esters differed from one another with respect to solubility in organic solvents and glass transition temperature, whereas all the random and ordered polymers were of equal low crystallinity. All of these polymers began to decompose around 350°C in both air and nitrogen atmospheres.     

The kinetics of polycondensation of α,α′‐dichloro‐p‐xylene with 4,4′‐isopropylidenediphenol using benzyltriethylammonium chloride as a phase‐transfer catalyst

The phase‐transfer catalyzed polycondensation of α,α′‐dichloro‐p‐xylene with 4,4′‐isopropylidenediphenol was carried out using benzylethylammonium chloride in a two‐phase system of an aqueous alkaline solution and benzene at 60 °C under nitrogen atmosphere. The rate of polycondensation was expressed as the combined terms of quaternary onium cation and 4,4′‐isopropylidenediphenolate anion rather than the feed concentration of catalyst and 4,4′‐isopropylidenediphenol. The measured concentrations of hydroxide and chloride anion in the aqueous solution and α,α′‐dichloro‐p‐xylene in the organic phase were used to obtain the reaction rate constant with the integral method, and to analyze the polycondensation mechanism with a cyclic phase‐transfer initiation step in the heterogeneous liquid–liquid system. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3059–3066, 2000     

Confinement of polystyrene at interfaces: Consequences on chain orientation

The knowledge of the structure and orientation of polymer chains adsorbed at an interface could be of major importance to predict the level of interfacial interactions and adhesion that depend strongly on the properties of the interface formed between the two materials (polymer and substrate) brought into contact. In this work, we were interested to study thin films of atactic polystyrene after adsorption (spin‐coating) on two chemically different substrates (inert and OH‐grafted gold substrates). The main aim is to analyze the resulting anisotropy due to the confinement in a quasi‐bidimensional geometry, as well as to investigate the incidence of the interfacial interactions, potentially established between the polymer and the surface, on the chain organization. Our infrared spectroscopy results allowed us to access the adsorption model of polystyrene chains and to highlight the relation between chain orientation and interfacial acid–base interactions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1268–1276, 2006