以四重氢键结合的超支化聚合物及其涂层材料

合成了以Upy(2-ureido-4[1H]-pyrimidone)封端的超支化聚合物并研究其涂层材料性能.首先在哌嗪与三羟甲基丙烷三丙烯酸酯摩尔比2.25∶1条件下,合成了端仲胺基超支化聚(酯-胺)(HPEA),进而在仲胺基/异氰酸酯基官能团比1∶0.3、1∶0.4和1∶0.5下,通过HPEA与单异氰酸酯基甲基异胞嘧啶反应,合成了一系列带有Upy基元的改性超支化聚合物.由于Upy基元间形成了自识别四重氢键,改性聚合物比HPEA具有更高的玻璃化转变温度和热分解温度,并且改性聚合物涂层具有优良的力学性能,这表明分子间强氢键相互作用可有效改善超支化聚合物的性能.     

具有四重氢键识别基元超支化聚合物的特殊流变行为

在羟基与异氰酸酯基官能团比1∶0.13、1∶0.25、1∶0.33和1∶0.5下,通过端羟基超支化聚(酯-胺)(HPEA)与单异氰酸酯基甲基异胞嘧啶的反应,合成了一系列以脲基嘧啶酮(ureidopyrimidinone,Upy)单元封端的超支化聚合物(HPEA-U).由于Upy单元间形成自识别四重氢键作用,Upy改性聚合物的熔融流变行为表现出了明显的温度和频率依赖性.随着Upy含量增加,聚合物的解缔温度逐渐增加.在低频范围内,随着频率增大,其表观黏度降低,储能模量增加.在临界频率以上,随着频率增大,出现剪切变稠及储能模量迅速降低现象.基于Upy微区结构的剪切破坏及游离Upy单元间的氢键结合,对这种特殊的流变行为进行了解释.     

具有四重氢键识别基元的超支化聚合物

在羟基/异氰酸酯基官能团比4∶1的条件下,通过超支化聚合物Boltorn H20(HPE)与Upy(ureidopyrimidinone)的反应,合成了带有四重氢键单元的改性超支化聚合物HPE-1.采用核磁共振仪及红外分析仪测定了HPE-1的结构.由于分子间强的相互作用,HPE-1在熔融状态下可拉丝,而HPE不能.由于分子中含有亲水的羟基和疏水的Upy基元,HPE-1在水中能够自组装成球状聚集体.在酸性溶液中聚集体变大,而在碱性溶液中聚集体破坏,这为制备敏感性材料提供了途径.     

Synthesis and thermal,optical, and mechanical properties of sequence‐controlled poly(1‐adamantyl acrylate)‐block‐poly(n‐butyl acrylate) containing polar side group

We prepared the sequence‐controlled block copolymers including poly(1‐adamantyl acrylate) (PAdA) and poly(n‐butyl acrylate) sequences as the hard and soft segments, respectively, by the organotellurium‐mediated living radical polymerization. The thermal, optical, and mechanical properties of the adamantane‐containing block copolymers with polar 2‐hydroxyethyl acrylate (HEA) and acrylic acid (AA) repeating units were investigated. The microphase‐separated structures of the block copolymers were confirmed by the differential scanning calorimetry and atomic force microscopy observations as well as dynamic mechanical measurements. The α‐ and β‐dispersions due to the main‐chain and side group molecular motions, respectively, of the hard and soft segments were observed. Their transition temperatures and activation energies increased due to the formation of intermolecular hydrogen bonding by the introduction of the HEA and AA repeating units. The effects of the hydrogen bonding on their tensile elasticity, strength, and strain were also evaluated. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2899–2910     

Self‐Assembly of Diblock Copolymers into Novel Snowflake‐Shaped Aggregates Driven by Quadruple Hydrogen Bonding

Two well‐defined diblock copolymers with quadruple hydrogen‐bonding groups on one block, denoted PSUEA‐1 and PSUEA‐2 , have been synthesized, and novel snowflake‐shaped nanometer‐scale aggregates, self‐assembled by such diblock copolymers in non‐polar solvents, have been observed. The micellar dimensions were investigated by DLLS and SLLS. Their morphologies were studied by TEM. Since the degrees of polymerization of the Upy‐containing blocks of PSUEA‐1 and PSUEA‐2 are quite similar and the polystyrene block of the PSUEA‐1 is longer than that of the PSUEA‐2 , a subtle but identifiable difference between the sizes and structures of the PSUEA‐1 and PSUEA‐2 aggregates was noticed and characterized.

     

Formation of polypseudorotaxane networks by cross-linking the quadruple hydrogen bonded linear supramolecular polymers via bisparaquat molecules

The creation of novel crown ether-paraquat polypseudorotaxane networks, constructed by bisparaquat monomers threading into the cavity of the crown ether units of linear supramolecular polymers that are formed based on the quadruple hydrogen bonded unit ureidopyrimidinone (Upy) in the concentrated solution, is described.     

Polymerization of 2‐hydroxyethyl acrylate in bulk and solution by chemical initiator and by ATRP method

In this study, 2‐hydroxyethyl acrylate (HEA) was polymerized to obtain polymers that can be used as hydrogel and copolymerized for biomedical applications. Bulk, solution, and atom transfer radical polymerization (ATRP) techniques at different temperatures were applied. The polymerization in bulk form was carried out in vacuum and in open atmosphere. The polymerization curves showed autoacceleration mechanism and the limiting conversion was 100%. The polymers obtained were insoluable in most common solvents because of high molecular weights and strong intermolecular hydrogen bonding. They absorb more than 30% (w/w) water as hydrogel. To decrease the molecular weight and obtain soluble polymers, HEA was polymerized in solution by ATRP method, which also gave insoluble hydrogel type polymers. The activation energy for bulk polymerization was 155.8 kJ/mol, which is very high for a free radical polymerization. This is due to the high degree of intermolecular hydrogen bonding, which was also supported by FTIR and TGA analysis. The polymers were characterized by FT‐IR, DSC, TGA, and ¹H NMR techniques. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3957–3965, 2005     

Versatile cobalt(Salen-NEt2) for aqueous cobalt-mediated radical polymerization

Cobalt-mediated radical polymerization (CMRP) has enabled the polymerization of a wide range of monomers with predictable molecular parameters and well-defined compositions and architectures. However, the synthesis of hydrophilic polymers by CMRP directly in the aqueous phase is still challenging. Herein, a handy cobalt complex was developed to perform CMRP of N-vinylpyrrolidone (NVP), 2-hydroxyethyl acrylate (HEA), and N,N-dimethylacrylamide (DMA) with linearly increased molecular weight, low polydispersity values, and smoothly shifted gel permeation chromatography (GPC) traces. The chain extensions of NVP, HEA, and DMA revealed the well chain-end fidelity for the synthesis of block copolymers. Moreover, the poly(N-vinylpyrrolidone)-block-poly(vinyl acetate) (PVP-b-PVAc) amphiphilic block copolymer colloidal solution was achieved directly in aqueous phase by cobalt-mediated radical polymerization-induced self-assembly (CMR-PISA), forming the nanoparticles consisting of a hydrophilic PVP corona and a hydrophobic PVAc core. This new mediator opens the opportunity for the synthesis of various hydrophilic (co)polymers in an environmentally friendly manner.     

Quadruple hydrogen bonding containing supramolecular thermoplastic elastomers: Mechanical and morphological correlations

We report the design of bioinspired, reversible supramolecular thermoplastic elastomers (TPEs) functionalized with ureido‐cytosine (UCyt) complementary quadruple hydrogen bonding (QHB) sites. The polymer contained a soft poly(n‐butyl acrylate) central block that imparted flexibility and two external, hard nucleobase‐containing blocks that contributed to structural integrity. In addition, the hard block with pendant QHB motifs served as efficient physical crosslinks to further enhance the thermomechanical performance, where the polymer service window extended up to 30 °C higher compared to the controls that bear dimeric hydrogen bonding units. The resulting UCyt copolymers also exhibited improved surface and bulk morphology, which self‐assembled into well‐ordered lamellar microstructures. Moreover, the polymer displayed an unexpected moisture‐resistant property with less than 1 wt % equilibrium moisture uptake even at 95% relatively humidity, which presumably correlated with its well‐ordered and densely‐packed morphology facilitated by strong hydrogen bonding. Variable temperature Fourier‐transform infrared spectroscopy experiments further confirmed the thermoreversibility of hydrogen bonding, indicating melt‐processablility and recyclability of the polymer. These physical properties verified quadruple bonding dominated behavior, and structure–property–morphology relationships suggest key design parameters for future TPEs. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 13–23     

Thermal degradation of vinylidene chloride/[4-(t-butoxycarbonyloxy)phenyl]methyl acrylate copolymers

Vinylidene chloride polymers containing comonomer units capable of consuming evolved hydrogen chloride to expose good radical-scavenging sites might be expected to display greater thermal stability than similar polymers containing simple alkyl acrylates as comonomer. Incorporation of a comonomer containing the phenyl t-butyl carbonate moiety into a vinylidene chloride polymer has the potential to afford a polymer with pendant groups which might interact with hydrogen chloride to expose phenolic groups. Copolymers of vinylidene chloride with [4-(t-butoxycarbonyloxy)phenyl]methyl acrylate have been prepared, characterized, and subjected to thermal degradation. The degradation has been characterized by thermal and spectroscopic techniques. The degradation of vinylidene chloride/[4-(t-butoxycarbonyloxy)phenyl]methyl acrylate copolymers is much more facile than the same process for similar copolymers containing either [4-(isobutoxycarbonyloxy)phenyl]methyl acrylate or methyl acrylate, a simple alkyl acrylate, as comonomer. During copolymer degradation, [4-(t-butoxycarbonyloxy) phenylmethyl acrylate units are apparently converted to acrylic acid units by extensive fragmentation of the sidechain. Thus, the phenyl t-butyl carbonate moiety does function as a labile acid-sensitive pendant group but its decomposition in this instance leads to the generation of a phenoxybenzyl carboxylate capable of further fragmentation.     

Oil-in-gold nanoparticle solution emulsion stabilized with amphiphilic polymers and its stability under NIR irradiation

Oil-in-water emulsions were prepared by emulsifying mineral oil in gold nanoparticle (GNP) solution using amphiphilic polymers as an emulsifier. Poly(2-hydroxyethyl acrylate) (PHEA) and poly(2-hydroxyethyl acrylate-co-propyl methacryate) (P(HEA/PMA)) having different PMA contents (2.98%, 3.29%, 6.1%, and 8.59% (mole/mole)) were prepared by a free radical polymerization, confirmed by ¹H NMR spectroscopy. According to the optical density change of the polymer solution (2% (w/v)) at 20°C–80°C, only P(HEA/PMA) having a PMA content of 3.29 mole % showed its lower solution critical temperature around 31°C. The air/water interfacial activity of the amphiphilic polymers was higher as the PMA content was higher. GNP was prepared by reducing gold ions in water. The mean hydrodynamic diameter was 22.2?nm and it appeared sphere-like on TEM photo. The emulsion prepared using PHEA maintained its stability above 80% for 190 hours, whereas it was destabilized rapidly upon 60 minutes of near-infrared (NIR) irradiation and its stability decreased to below 20% in 20 hours. As the PMA content was higher, the stability of the emulsions prepared using P(HEA/PMA) became lower and NIR irradiation accelerated the destabilization more effectively.     

Tunable thermoresponsive β-cyclodextrin-based star polymers

Thermoresponsive star polymers were synthesized by copolymerization of water-soluble acrylate monomers, di(ethylene glycol) ethyl ether acrylate (DEGA) and 2-hydroxyethyl acrylate (HEA), in a core-first approach using a modified β-cyclodextrin multifunctional initiator and photo-mediated atom transfer radical polymerization (photoATRP). The controlled character of the polymerization, as well as the formation of statistical star copolymers, was demonstrated. The lower critical solution temperature (LCST) is conveniently tuned by varying the ratio of the two hydrophilic monomers. The cyclodextrin core appears to lead to a lowering of the LCST, and introduction of a hydrophobic pocket via star block copolymer synthesis allowed for further tunability of the cloud point temperature. In the final step, we demonstrate that the star polymers made in here can be used as facile carriers and solubilizers for hydrophobic compounds, highlighting their applicability in the biomedical field.     

Synthesis of acrylic rosin derivatives and application as negative photoresist

Functional monomers containing a rosin moiety, maleopimaric acid anhydride (MPA) and fumaropimaric acid (FPA) were synthesized from gum rosin. Monofunctional acrylic rosin derivatives were synthesized from esterification of MPA and various acrylates, (2-hydroxyethyl acrylate) (HEA), 3-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate. Monofunctional monomers were copolymerized with (methyl methacrylate) (MMA) by radical polymerization. Trifunctional acrylate was synthesized from FPA and HEA. All the monomers and polymers showed good solubility and low absorbance in the UV region (200-400 nm). Negative patterns from rosin derivatives were obtained by two methods, one is a photocuring method using trifunctional acrylate and copolymers, and the other is photocrosslinking of copolymers using a photocrosslinker under UV (I-line) radiation. Negative photoresists containing rosin moiety showed high contrast and minimum linewidth of 2.2 μm.     

Polymer electrolyte membranes based on polystyrenes with phosphonic acid via long alkyl side chains

A series of polystyrenes with phosphonic acid ( 5 ) via long alkyl side chains (4, 6, and 8 methylene units) were prepared by the radical polymerization of the corresponding diethyl ω‐(4‐vinylphenoxy)alkylphosphonates, followed by the hydrolysis with trimethylsilyl bromide. The resulting phosphonated polystyrene membranes had a high oxidative stability against Fenton's reagent at room temperature. The membranes prepared from 5 exhibited a very low water uptake, similar to that of Nafion 117 over the wide range of 30 to 80% relative humidity (RH). The proton conductivities of these membranes are lower than that of Nafion 117 in the range of 30 to 90% RH, but comparable or higher than those of the reported phosphonated polymers with higher IEC values, such as the phosphonated poly(N‐phenylacrylamide) (PDPAA, IEC: 6.72 mequiv/g) and fluorinated polymers with pendant phosphonic acids (M47, IEC: 8.5 mequiv/g), at low RH conditions despite the much lower IEC values (3.0–3.8 mequiv/g) of these membranes. These results suggest that the flexible pendant side chains of 5 would contribute to the formation of hydrogen‐bonding networks by considering the very low water uptake of these polymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Quadruple Hydrogen Bond-Containing A-AB-A Triblock Copolymers: Probing the Influence of Hydrogen Bonding in the Central Block

This work reveals the influence of pendant hydrogen bonding strength and distribution on self-assembly and the resulting thermomechanical properties of A-AB-A triblock copolymers. Reversible addition-fragmentation chain transfer polymerization afforded a library of A-AB-A acrylic triblock copolymers, wherein the A unit contained cytosine acrylate (CyA) or post-functionalized ureido cytosine acrylate (UCyA) and the B unit consisted of n-butyl acrylate (nBA). Differential scanning calorimetry revealed two glass transition temperatures, suggesting microphase-separation in the A-AB-A triblock copolymers. Thermomechanical and morphological analysis revealed the effects of hydrogen bonding distribution and strength on the self-assembly and microphase-separated morphology. Dynamic mechanical analysis showed multiple tan delta (δ) transitions that correlated to chain relaxation and hydrogen bonding dissociation, further confirming the microphase-separated structure. In addition, UCyA triblock copolymers possessed an extended modulus plateau versus temperature compared to the CyA analogs due to the stronger association of quadruple hydrogen bonding. CyA triblock copolymers exhibited a cylindrical microphase-separated morphology according to small-angle X-ray scattering. In contrast, UCyA triblock copolymers lacked long-range ordering due to hydrogen bonding induced phase mixing. The incorporation of UCyA into the soft central block resulted in improved tensile strength, extensibility, and toughness compared to the AB random copolymer and A-B-A triblock copolymer comparisons. This study provides insight into the structure-property relationships of A-AB-A supramolecular triblock copolymers that result from tunable association strengths.     

Hybrid Copolymerization via the Combination of Proton Transfer and Ring-opening Polymerization

Phosphazene base,t-BuP2,was employed to catalyze the proton transfer polymerization(PTP)of 2-hydroxyethyl acrylate(HEA),and PTP was further combined with ring-opening polymerization(ROP)to exploit a new type of hybrid copolymerization.The studies on homopolymerization showed that t-BuP2 was a particularly efficient catalyst for the polymerization of HEA at room temperature,giving an excellent monomer conversion.Throughout the polymerization,transesterification reactions were unavoidable,which increased the randomness in the structures of the resulting polymers.The studies on copolymerization showed that t-BuP2 could simultaneously catalyze the hybrid copolymerization via the combination of PTP and ROP at 25°C.During copolymerization,HEA not only provided hydroxyl groups to initiate the ROP ofε-caprolactone(CL)but also participated in the polymerization as a monomer for PTP.The copolymer composition was approximately equal to the feed ratio,demonstrating the possibility to adjust the polymeric structure by simply changing the monomer feed ratio.This copolymerization reaction provides a simple method for synthesizing degradable functional copolymers from commercially available materials.Hence,it is important not only in polymer chemistry but also in environmental and biomedical engineering.     

Synthesis and characterizations of the four‐armed amphiphilic block copolymer S[poly(2,3‐dihydroxypropyl acrylate)‐block‐poly(methyl acrylate)]4

The polymers poly[(2,2‐dimethyl‐1,3‐dioxolane‐4yl) methyl acrylate] (PDMDMA) and four‐armed PDMDMA with well‐defined structures were prepared by the polymerization of (2,2‐dimethyl‐1,3‐dioxolane‐4yl) methyl acrylate (DMDMA) in the presence of an atom transfer radical polymerization (ATRP) initiator system. The successive hydrolyses of the polymers obtained produced the corresponding water‐soluble polymers poly(2,3‐dihydroxypropyl acrylate) (PDHPA) and four‐armed PDHPA. The controllable features for the ATRP of DMDMA were studied with kinetic measurements, gel permeation chromatography (GPC), and NMR data. With the macroinitiators PDMDMA–Br and four‐armed PDMDMA–Br in combination with CuBr and 2,2′‐bipyridine, the block polymerizations of methyl acrylate (MA) with PDMDMA were carried out to afford the AB diblock copolymer PDMDMA‐b‐MA and the four‐armed block copolymer S{poly[(2,2‐dimethyl‐1,3‐dioxolane‐4yl) methyl acrylate]‐block‐poly(methyl acrylate)}₄, respectively. The block copolymers were hydrolyzed in an acidic aqueous solution, and the amphiphilic diblock and four‐armed block copolymers poly(2,3‐dihydroxypropyl acrylate)‐block‐poly(methyl acrylate) were prepared successfully. The structures of these block copolymers were verified with NMR and GPC measurements. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3062–3072, 2001     

Studies on the Preparation of Stable and High Solid Content Emulsifier-Free Poly(MMA/BA/HEA) Latex with the Addition of AMPS and Characterization of the Obtained Copolymers

The 2-acrylamido -2-methylpropane sulfonic acid (AMPS) was used as a reactive comonomer for the methyl methacrylate (MMA), n-butyl acrylate (BA) and 2-hydroxyethyl acrylate (HEA) emulsifier-free emulsion copolymerization system to obtain latices of stable and high-solid content (50 wt%).The polymerization and storage process is very stable, and the emulsion could store at room temperature for more than six months with the addition of AMPS. Properties of the latices, such as stability, flow behavior, particles diameter and morphology were studied. In addition, physical properties of the obtained copolymers, such as water resistance, glass transition temperature (T_g) were also investigated. The final size of the latex particles is 200～300 nm in diameter. Compared with the copolymers that were prepared by surfactant emulsion polymerization water resistance is greatly improved.     

Control of thermal,mechanical, and optical properties of three‐component maleimide copolymers by steric bulkiness and hydrogen bonding

N‐substituted maleimides polymerize in the presence of a radical initiator to give polymers with excellent thermal stabilities and transparency. In this study, we synthesized various maleimide copolymers with styrenes and acrylic monomers to control their thermal and mechanical properties by the introduction of bulky substituents and intermolecular hydrogen bonding. Three‐component copolymers of N‐(2‐ethylhexyl)maleimide in combination with styrene, α‐methylstyrene (MSt), or 1‐methylenebenzocyclopentane (BC5) as the styrene derivatives, and n‐butyl acrylate, 2‐hydroxyethyl acrylate, 4‐hydroxybutyl acrylate, or acrylic acid as the acrylic monomers were prepared by radical copolymerization. These copolymers were revealed to exhibit excellent heat resistance by thermogravimetric analysis. Glass transition temperatures increased by the introduction of bulky MSt and BC5 repeating units. The mechanical properties of the copolymer films were improved by the introduction of intermolecular hydrogen bonding. Optical properties, such as transmittance, refractive index, Abbe number, and birefringence, were determined for the copolymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1569–1579     

Amphiphilic block copolymers containing thermally degradable poly(phthalaldehyde) blocks

In this study, the preparation of a new class of amphiphilic block copolymers consisting of a poly(phthalaldehyde) (PPA) block and hydrophilic poly(alkylene oxide) blocks is described. PPA was prepared by ionic cyclopolymerization. A telechelic polymer block was prepared by endcapping of the PPA by a bifunctional reagent carrying isocyanate and isothiocyanate groups. As the second block, monoamino‐terminated poly(alkylene oxide)s (Surfonamines®, also known as Jeffamines®) were chosen. These polymers could be readily coupled to the PPA telechel and gave amphiphlic, mainly ABA‐type block copolymers. The PPA block of these products can be selectively depolymerized at moderate temperature. The block copolymers were characterized by dual‐detection size exclusion chromatography, and the defined and stepwise thermal decomposition of the two different block types were shown by thermogravimetric analysis. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1499–1509, 2009