Chain-growth Condensation Polymerization Research Articles

Synthesis of well‐defined aromatic poly(amide‐ether)s via chain‐growth condensation polymerization

AbstractSince their advent over 50 years ago, aromatic polyamides have remained desirable for their thermal stability, mechanical strength, and overall versatility. Chain‐growth condensation (CGC) polymerization has made possible the synthesis of well‐defined polyamides with narrow molecular weight distributions for applications ranging from block copolymers to polymer brushes. However, the solubility of aromatic polyamides has always been a major obstacle to overcome due to aromatic π‐π stacking and intramolecular hydrogen bonding. In this article, we introduce an aryl ether functionality into the polyamide backbone to increase backbone flexibility and overall solubility. Through dropwise addition of the aryl ether functionalized monomer with a lithium disilazide base and a phenyl 4‐(dimethylcarbamoyl)benzoate initiator, we report the synthesis of a series of substituted poly(amide‐ether)s through CGC polymerization with low polydispersities (<1.1) and well‐defined molecular weights. Computational methods revealed that the polymerization mechanism is unlike other similar amino ester monomers bearing naphthalene and biphenyl aromatic units in that monomer self‐deactivation is weakened by the ether linkage. The self‐condensation of the amide‐ether monomer was nevertheless suppressed through reaction optimization, challenging the traditional requirement of monomer self‐deactivation to achieve a well‐defined CGC polymerization. The side‐chain on poly(amide‐ether) backbone was also modified from an octyl group to a 4‐(octyloxy)benzyl protecting group for postpolymerization removal with trifluoroacetic acid to yield the unsubstituted aromatic poly(amide‐ether), which showed a significant improvement in solubility from traditional unsubstituted aromatic polyamides, such as poly(p‐benzamide).

Aromatic Polyamide Brushes for High Young’s Modulus Surfaces by Surface-Initiated Chain-Growth Condensation Polymerization

Aromatic Polyamide Brushes for High Young’s Modulus Surfaces by Surface-Initiated Chain-Growth Condensation Polymerization

Antifouling Oligoethylene Glycol-Functionalized Aromatic Polyamides Brushes Synthesized via Surface-Initiated Chain-Growth Condensation Polymerization

Antifouling Oligoethylene Glycol-Functionalized Aromatic Polyamides Brushes Synthesized via Surface-Initiated Chain-Growth Condensation Polymerization

Visible Light Induced Conventional Step-Growth and Chain-Growth Condensation Polymerizations by Electrophilic Aromatic Substitution.

A novel visible light induced step-growth polymerization by electrophilic aromatic substitution between photochemically generated carbocations and dimethoxybenzene nucleophile is described. Conventional step-growth polymerization and chain-growth condensation polymerization (CCP) mechanisms are presented. It is found that by changing the molar ratios of the monomers slightly, the CCP mechanism becomes operative and relatively higher molecular weight polymers are obtained because of the higher reactivity of the end groups of the intermediates and oligomers than that of the monomers. The possibility of grafting onto polymers containing epoxide at their side chains by photoinduced chain end activation of poly(dimethoxyphenylene methylene) is demonstrated. This study is expected to promote potential applications of the combination of photoinduced electron transfer reactions and CCP in macromolecular synthesis and material science.

Well-Defined Dual Light- and Thermo-Responsive Rod-Coil Block Copolymers Containing an Azobenzene, MEO2MA and OEGMA.

Here we report the dual light- and thermo-responsive behavior of well-defined rod-coil block copolymers composed of an azobenzene unit, 2-(2-methoxyethoxy)ethyl methacrylate (MEO2MA) and oligo(ethylene glycol) methacrylate (OEGMA). Azobenzene-containing rigid rod blocks prepared by chain growth condensation polymerization of the azobenzene containing monomer were used as a macroinitiator of atom transfer radical polymerization (ATRP) after attaching an α-bromoisobutyryl group as an end group. Synthesis of well-defined rod-coil block copolymers with different coil block lengths was achieved by copolymerization of MEO2MA and OEGMA monomers. The synthesized polymers exhibited amphiphilic properties and polymeric micelles were formed in aqueous solution. The light-responsive behaviors of azobenzene moieties, photoisomerization by irradiation of light, and thermo-responsive behaviors of P(MEO2MA-co-OEGMA) coil blocks, aggregation by increment of temperature over lower critical solution temperature, were investigated. A dual stimuli-responsive behavior of the rod-coil block copolymers was observed when exposed to light and heat.

Well-defined poly(ether sulfone)-b-polylactide: synthesis and microphase separation behavior

We investigated the microphase separation behavior of well-defined poly(arylene ether sulfone)-b-polylactide (PES-b-PLA) diblock copolymers. PES was synthesized by the nucleophilic aromatic substitution polymerization of 4-fluoro-4′-hydroxydiphenyl sulfone potassium salt in the presence of an allyl-functionalized initiator, which follows a chain growth condensation polymerization mechanism. A hydroxyl group installed via a thiol-ene reaction was utilized as the initiating site for the ring opening polymerization of d,l-lactide, producing the target polymer. The polymers were further purified by preparative size-exclusion chromatography and analyzed by small-angle X-ray scattering with temperature variations from room temperature to 150 °C. The PES block was glassy in the employed temperature range, but the PLA chains provided sufficient mobility for ordering of the block copolymer when PES was the minor fraction. An order-disorder transition (ODT) with changing temperature could not be located because PLA was not stable above 170 °C. From the degree of polymerization values of the polymers near the ODT, the Flory–Huggins interaction parameter, χ, could be roughly estimated as 0.12 at 150 °C. This high χ value suggests that engineering plastic-containing block copolymers could be useful in advanced lithographic and filtration applications. Well-defined poly(arylene ether sulfone)-b-polylactides (PES-b-PLAs) were successfully synthesized and their microphase separation behavior was investigated. PES was obtained via chain growth condensation polymerization, and subsequent end group modification followed by ring opening polymerization of d,l-lactide produced the diblock copolymers. By small-angle X-ray scattering experiments in bulk, the formation of ordered morphologies including spherical, cylindrical, gyroidal, and lamellar was observed. An effective interaction parameter at 150 °C was roughly estimated as 0.12 for the first time in engineering plastic-containing block copolymers.

Synthesis and self-assembly of Poly(N-octyl benzamide)-μ-poly(ε-caprolactone) miktoarm star copolymers displaying uniform nanofibril morphology

In this study, we employed an efficient strategy by the combinations of chain-growth condensation polymerization (CGCP), styrenics-assisted atom transfer radical coupling (SA ATRC), and ring-opening polymerization (ROP) to synthesize novel miktoarm (μ) star copolymers. Accordingly, poly(N-octyl benzamide) (PBA) and poly(ε-caprolactone) (PCL) arms were conjugated to form μ-(PBA)2(PCL)m star (m = ca. 4; Mn = ca. 13400; Đ = 1.17; abbr.: μ-(PBA)(PCL)). Thermal properties of homopolymers and μ-(PBA)(PCL) were examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). In μ-(PBA)(PCL) star copolymer, notably, an increased Tg of PBA chain (26.3 °C) was detected as well as the melting behavior in Tm (44.8 °C) and the peak profile were significantly changed. It might be due to topological influence on the restriction of both chain mobility and crystallinity. The behaviors of slow crystallization and low crystallinity of μ-(PBA)(PCL) star can be revealed by polarized optical microscopy (POM) and Fourier-transform infrared spectroscopy (FT-IR). We then analyzed morphology of drop-casting thin films of PCL, PBA, and μ-(PBA)(PCL) (co)polymers on Si wafer by atomic force microscopy (AFM). Casting by 1 wt% μ-star solution, we obtained uniform and clear nanofibers with an average diameter of ca. 20 nm. Using grazing-incidence X-ray diffractometer (GI XRD), orthorhombic (110) and (200) diffraction peaks were clear observed. In addition, grazing-incidence small-to-wide angle X-ray diffractometer (GI SWAXS) of μ-(PBA)(PCL) thin film displayed diffraction peaks composed of q/q* peaks of 1:√3 with a periodic size of approximately 16.1 nm that revealed the diameter of the nanofibril morphology.

Synthesis and phase transition behavior of well-defined Poly(arylene ether sulfone)s by chain growth condensation polymerization in organic media

A series of well-defined poly(arylene ether sulfone)s (PESs) as a rod-type block was synthesized by chain-growth condensation polymerization from a diphenyl sulfone-type initiator containing a fluorine leaving group and an allyl moiety. Interestingly, these oligomeric PESs exhibited lower critical solution temperature (LCST)-type phase transition behavior in organic solvents, i.e., 1,2-dimethoxyethane (DME) and chloroform. The clouding point temperature was affected by the molecular weight and concentration of the polymers. The cloud temperature decreased as the molecular weight polymers and the concentration of polymer solution increased. And also two series of rod-coil type poly(arylene ether sulfone)-b-polylactides were synthesized by controlled ring-opening esterification polymerization of dl-lactide with a PES-derived macroinitiator in which the allyl group was transformed into an aliphatic hydroxyl group by a thiol-ene click reaction. These diblock copolymers also exhibited LCST behavior in DME, and the nanoscale size of the aggregates increased upon heating.

Synthesis of Poly(N-H benzamide)-b-poly(lauryl methacrylate)-b-poly(N-H benzamide) symmetrical triblock copolymers by combinations of CGCP, SARA ATRP, and SA ATRC

We design a novel ABA type triblock copolymer (triBCP) by performing efficient synthetic methods of chain-growth condensation polymerization (CGCP), supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP), and styrenics-assisted atom transfer radical coupling (SA ATRC). A well-defined poly(3-(N-(octyloxy)benzyl benzamide) having a 2-bromo-2-phenylacetate effective ATRP initiating site (i.e., POOBBA-BrPA) through CGCP following quantitative chain end modifications, was firstly synthesized. The POOBBA-BrPA macroinitiator then conducted chain extension with lauryl methacrylate (LMA) via SARA ATRP to obtain the POOBBA-b-PLMA-Br diBCP (Mn = 8800 and Mw/Mn = 1.15). This was followed by SA ATRC of POOBBA-b-PLMA-Br with a high extent of coupling (xc = 0.85, Mn = 15300, and Mw/Mn = 1.26). The obtained triBCP was further purified and the selective removal of the protecting group yielded poly(N-H benzamide)-b-poly(lauryl methacrylate)-b-poly(N-H benzamide) (i.e., PNHBA-b-PLMA-b-PNHBA) was conducted. The characterization of these copolymers was performed using 1H NMR, GPC, FT-IR, TGA, DSC, AFM and SAXS.

Synthesis of Well-Defined Poly(N-H Benzamide-co-N-Octyl Benzamide)s and the Study of their Blends with Nylon 6.

We synthesized a series of copolybenzamides (PBA) through chain-growth condensation polymerization (CGCP) of 4-(octylamino)benzoate (M4OB) and methyl 3-(4-(octyloxy)benzylamino) benzoate (M3OOB) co-monomers. Well-defined copolybenzamides with close to theoretical molecular weights (Mn ≈ 10,000–13,000) and narrow molecular weight distributions (Mw/Mn < 1.40) were obtained. Selective removals of the protecting group (i.e., 4-(octyloxy)benzyl group) from the affording P(M3OOB-co-M4OB) copolybenzamides were subsequently performed to obtain P(M3NH-co-M4OB) copolymers. These novel N-H-containing copolybenzamides (named as PNHBA) can not only provide hydrogen bonds for polymer-polymer blends but also have good solubility in organic solvents. Miscibility of the PNHBA and Nylon 6 blends was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), FT-IR, contact angle analysis, transmission electron microscope (TEM), and dynamic mechanical analysis (DMA). This study illustrates a novel type of copolybenzamide with controlled molecular weight and narrow molecular weight distribution through an effective synthetic strategy, and can be applied to a practical blend of Nylon 6 with good miscibility.

Synthesis of Novel μ-Star Copolymers with Poly(N-Octyl Benzamide) and Poly(ε-Caprolactone) Miktoarms through Chain-Growth Condensation Polymerization, Styrenics-Assisted Atom Transfer Radical Coupling, and Ring-Opening Polymerization.

Star copolymers are known to phase separate on the nanoscale, providing useful self-assembled morphologies. In this study, the authors investigate synthesis and assembly behavior of miktoarm star (μ-star) copolymers. The authors employ a new strategy for the synthesis of unprecedented μ-star copolymers presenting poly(N-octyl benzamide) (PBA) and poly(ε-caprolactone) (PCL) arms: a combination of chain-growth condensation polymerization, styrenics-assisted atom transfer radical coupling, and ring-opening polymerization. Gel permeation chromatography, mass-analyzed laser desorption/ionization mass spectrometry, and 1 H NMR spectroscopy reveal the successful synthesis of a well-defined (PBA11 )2 -(PCL15 )4 μ-star copolymer (Mn,NMR ≈ 12 620; Đ = 1.22). Preliminary examination of the PBA2 PCL4 μ-star copolymer reveals assembled nanofibers having a uniform diameter of ≈20 nm.

Chain-growth condensation polymerization of 5-aminoisophthalic acid triethylene glycol ester to afford well-defined, water-soluble, thermoresponsive hyperbranched polyamides

Based on a model amidation reaction of benzoic acid triethylene glycol (TEG) ester with lithium anilide, which proceeded as rapidly as that of the methyl ester and faster than that of the ethyl ester, we considered that a TEG ester AB2 monomer would have sufficient reactivity to undergo chain-growth condensation polymerization. Indeed, condensation polymerization of 5-(methylamino)isophthalic acid TEG ester proceeded in a chain-growth polymerization manner in the presence of 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS) and an initiator at −40 °C to afford a well-defined hyperbranched polyamide (HBPA) bearing many hydrophilic TEG ester moieties. The Mn values of the HBPA increased in proportion to the feed ratio of monomer to the initiator, with retention of low polydispersity (Mn = 6120–42200, Mw/Mn = 1.10–1.20). The degree of branching (DB) remained in the range of 0.48–0.51, irrespective of the feed ratio. A 0.25 wt% aqueous solution of HBPAs with different Mn values showed thermoresponsive behavior with a lower critical solution temperature (LCST) in the range of 35–37 °C, which is close to human body temperature, as in the case of poly(N-isopropylacrylamide).

Chain‐growth condensation polymerization approach to synthesis of well‐defined polybenzoxazole: Importance of higher reactivity of 3‐amino‐4‐hydroxybenzoic acid ester compared to 4‐amino‐3‐hydroxybenzoic acid ester

ABSTRACTApplication of chain‐growth condensation polymerization (CGCP) to obtain well‐defined polybenzoxazole (PBO) was examined. CGCP of both phenyl 3‐{(2‐methoxyethoxy)methoxy (MEM‐oxy)}‐4‐(octylamino)benzoate (1b) (para‐substituted monomer) and phenyl 4‐MEM‐oxy‐3‐(octylamino)benzoate (3b) (meta‐substituted monomer) was examined in the presence of metal disilazide base and phenyl 4‐nitro‐ or methylbenzoate 2 as an initiator. Polymerization of the latter monomer, but not the former, afforded polymer with controlled molecular weight based on the feed ratio of monomer to initiator and with a narrow molecular weight distribution. Accordingly, monomer 3c, in which the octyl group on the amino nitrogen of 3b was replaced with a 4‐(octyloxy)benzyl (OOB) group, was polymerized in the presence of lithium 1,1,1,3,3,3‐hexamethyldisilazide (LiHMDS), phenyl 4‐methylbenzoate (2b), and LiCl in THF at 0 °C to yield poly3c with well‐defined molecular weight (Mn = 4520–9080) and low polydispersity (Mw/Mn ≤ 1.11). Treatment of poly3c with trifluoroacetic acid simultaneously removed the MEM and OOB groups, affording poly(o‐hydroxyamide) (poly4) without scission of the amide linkages. Cyclodehydration of poly4 proceeded at 350 °C to yield PBO (poly5), which was insoluble in organic solvents and acids. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1730–1736

ChemInform Abstract: Scope of Controlled Synthesis via Chain‐Growth Condensation Polymerization. From Aromatic Polyamides to π‐Conjugated Polymers

AbstractReview: 159 refs.

Synthesis of Telechelic Poly(ether sulfone) Oligomers by Chain-Growth Condensation Polymerization

The synthesis of telechelic poly(ether sulfone)s with methoxy end groups is reported. Molecular weights ranging from 1600 to 2800 g mol −1 and polydispersities of 1.1–1.2 are synthesized by chain-growth condensation polymerization. The initiator is chosen by using semiempirical calculations and 19 F NMR spectroscopy measurements. The polymers are characterized by NMR spectroscopy and matrix-assisted laser desorption/ionization time of fl ight (MALDI-TOF) mass spectrometry (MS), and are terminated by a methoxy group at one end and a fl uorine at the other, and up to approximately 20% polymer of similar mass but slightly higher polydispersity, methoxy terminated at both ends, is present, along with less than 5% of polymer terminated at both ends by fl uorine atoms. These do not need to be separated, and can be converted to methoxy-ending telechelic blocks, yielding polyvalent, reactive rigid building blocks for copolymer synthesis.

Synthesis and optical properties of poly(p-benzamide)s bearing oligothiophene on the amide nitrogen atom through an alkylene spacer

Phenyl 4-((5′′-hexyl-2,2′-bithienyl)methyl)aminobenzoate (M1), phenyl 4-((5′′-hexyl-2,2′-bithienyl)propyl)aminobenzoate (M2) and phenyl 4-((5-hexyl-2,2′:5′,2′′-terthienyl)propyl)aminobenzoate (M3), each having oligothiophene on the nitrogen atom through the use of an alkylene spacer, were synthesized using a method in which the oligothiophene group was introduced by the reductive amination (M1) or the nucleophilic substitution (M2 and M3). The condensation polymerization was performed by adding the monomer and 4′-nitrophenyl 4-methylbenzoate to lithium bis(trimethylsilyl)amide and N,N,N′,N′-tetramethylethylenediamine (Method A). Poly(p-benzamide)s with number-averaged molecular weights ranging from 4400–7300 were obtained in high yields (∼80%). From the gel permeation chromatography profiles and the 1H-nuclear magnetic resonance spectra, the polymerization was found to proceed in a controlled manner. The C=O stretching vibration signal in the infrared spectra indicated the cis conformation of the amide group in the polymer backbone. However, the direct polycondensation of 4-((5′′-hexyl-2,2′-bithienyl)methyl)aminobenzoic acid using PPh3 and hexachloroethane in pyridine produced a cyclic trimer, that is, p-calix[3]amide (Method B). In contrast to polyM2 and p-calix[3]amide, a broad emission peak at ∼480 nm was observed for polyM1, indicating the π-stacked interaction between the bithiophene chromophores. As polyM3 (having the terthiophene) also exhibited a redshift of the emission maxima, the wide conjugated system was found to be susceptible to the strong π-stacked interaction at the polymer side chain. Three poly(p-benzamide)s bearing oligothiophene on the amide nitrogen atom through the alkylene spacer were prepared by the chain-growth condensation polymerization using initiator and base in the presence of chelating reagent. The polymerization was found to proceed in the controlled manner as confirmed by the GPC and NMR analyses. The UV and PL measurements indicated that the p-stacked interaction between oligothiophene chromophores depended on the structure of the repeating unit.

Synthesis of well-defined aromatic polyamide-graft-poly(tetrahydrofuran) by chain-growth condensation polymerization of macromonomer

Well-defined aromatic polyamide grafted with poly(tetrahydrofuran) [poly(THF)] is obtained by the chain-growth condensation polymerization of 4-aminobenzoic acid ester macromonomers 1 bearing poly(THF) on the amino group. The macromonomers are easily prepared by the reaction of living poly(THF) with 4-aminobenzoic acid ester. Polymerization of phenyl ester monomer 1a at −10 °C is accompanied by self-polycondensation, whereas that of methyl ester monomer 1b at 10 °C proceeds exclusively in a chain-growth polymerization manner.

Synthesis of polystyrene‐graft‐poly(p‐benzamide) by chain‐growth condensation polymerization and radical polymerization: Improvement of thermal properties of polystyrene

Synthesis of polystyrene‐<i>graft</i>‐poly(<i>p</i>‐benzamide) by chain‐growth condensation polymerization and radical polymerization: Improvement of thermal properties of polystyrene

Scope of controlled synthesis via chain-growth condensation polymerization: from aromatic polyamides to π-conjugated polymers

Conventional condensation polymerization proceeds in a step-growth polymerization manner, in which the generated polymers possess a broad molecular weight distribution, and control over molecular weight and polymer end groups is difficult. However, the mechanism of condensation polymerization of some monomers has been converted from step-growth to chain-growth by means of activation of the polymer end group, either due to the difference in substituent effects between the monomer and the polymer, or due to successive intramolecular transfer of catalyst to the polymer end. In this article, we review recent developments in chain-growth condensation polymerization (CGCP) in these two areas. The former approach has yielded many architectures containing aromatic polyamides and aromatic polyethers, with unique properties. In the latter case, the mechanism, catalysts, and initiators of Ni- and Pd-catalyzed coupling polymerizations leading to poly(alkylthiophene)s and poly(p-phenylene)s have been extensively investigated. Other well-defined π-conjugated polymers, such as polyfluorenes, n-type polymers, and alternating aryl polymers, have also been synthesized by means of catalyst-transfer condensation polymerization. Many π-conjugated polymer architectures prepared by utilizing catalyst-transfer condensation polymerization are not covered in this article.

Three‐arm star block copolymers of aromatic polyether and polystyrene from chain‐growth condensation polymerization, atom transfer radical polymerization, and click reaction

AbstractWell‐defined (AB)3 type star block copolymer consisting of aromatic polyether arms as the A segment and polystyrene (PSt) arms as the B segment was prepared using atom transfer radical polymerization (ATRP), chain‐growth condensation polymerization (CGCP), and click reaction. ATRP of styrene was carried out in the presence of 2,4,6‐tris(bromomethyl)mesitylene as a trifunctional initiator, and then the terminal bromines of the polymer were transformed to azide groups with NaN3. The azide groups were converted to 4‐fluorobenzophenone moieties as CGCP initiator units by click reaction. However, when CGCP was attempted, a small amount of unreacted initiator units remained. Therefore, the azide‐terminated PSt was then used for click reaction with alkyne‐terminated aromatic polyether, obtained by CGCP with an initiator bearing an acetylene unit. Excess alkyne‐terminated aromatic polyether was removed from the crude product by means of preparative high performance liquid chromatography (HPLC) to yield the (AB)3 type star block copolymer (Mn = 9910, Mw/Mn = 1.10). This star block copolymer, which contains aromatic polyether segments with low solubility in the shell unit, exhibited lower solubility than A2B or AB2 type miktoarm star copolymers. In addition, the obtained star block copolymer self‐assembled to form spherical aggregates in solution and plate‐like structures in film. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012