Recent Research Progress of Branched and Functional Branched Polyethylene Prepared Using Ni- and Pd–Based Catalysts

In this paper, the recent development of branched and functional branched polyethylene prepared using Ni- and Pd-based catalysts are reviewed. The influence of ligand species, steric effect, electronic effect and polymerization condition on branching density of resultant polymer prepared using Ni- and Pd-based catalysts is discussed. In addition, the review is also focused on functional branched polyethylene produced by copolymerization of ethylene and polar monomer and copolymerization mechanism.     

A novel strategy to branched polyacrylonitrile via one‐pot RAFT copolymerization of acrylonitrile and an asymmetrical divinyl monomer

Branched polyacrylonitriles were prepared via the one‐pot radical copolymerization of acrylonitirle and an asymmetric divinyl monomer (allyl methacrylate) that possesses both a higher reactive methacrylate and a lower reactive allyl. RAFT technique was used to keep a low‐propagation chain concentration via a fast reversible chain transfer euilibration and thus the cross‐linking was prevented until a high level of monomer conversions. This novel strategy was demonstrated to engenerate a branched architecture with abundant pendant functional vinyl and nitrile groups, and controlled molecular weight as a behavior of controlled/living radical polymerization characteristics. The effect of the various experimental parameters, including temperature, brancher to monomer molar ratio, and chain transfer agent to initiator molar ratio, on the control of moleculer dimension (molecular weight and polydispersity indices) and the degree of branching were investigated in detail. Moreover, ¹H NMR and gel permeation chromatography confirm the branched architecture of the resultant polymer. The intrinsic viscosity of the copolymer is also lower than the linear counterpart.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

支化聚合物皮革复鞣填充剂的制备及应用

以甘油(Gly)和马来酸酐(MA)为原料合成马来酸甘油酯(MG),作为多官能度烯类支化单体与丙烯酸(AA)单体,通过自由基共聚法制备水性支化聚合物皮革复鞣填充剂(BPMG)。通过1HNMR对支化单体和聚合物的结构进行了表征。通过正交实验考察了单体配比、引发剂用量、支化单体类型和投料方式对MG双键转化率的影响。结果表明,MG-30为支化单体,n(AA)∶n(MG)=6∶1,w(过硫酸铵)=6%时,以单体滴加的方式,聚合温度85℃,聚合时间2.5h的条件下,具有较高的双键转化率。应用结果显示支化聚合物可以提供皮革较好的填充性能和力学性能。SEM结果表明,支化聚合物对皮革纤维具有明显的分散作用。     

Synthesis and gas transport properties of novel poly(aryl ether ketone)s with branched structure

Poly(aryl ether ketone)s (PAEKs) based on 2‐(3′‐trifluoromethylphenyl) hydroquinone and 4,4′‐difluorobenzophenone were synthesized and characterized in the presence or absence of 2,4′,6‐trifluorobenzophenone (BB′₂ monomer). The influence of the incorporation of a branched structure (BB′₂ monomer) on the gas transport properties of PAEKs was investigated. The results showed that PAEKs with a branched structure possess a higher permeability and selectivity than PAEKs without a branched structure. Moreover, improvements in the permeability and selectivity were enhanced with increasing content of BB′₂ monomer. This synergistic effect on permeability and selectivity was mainly due to the higher fractional free volume and the unique size and distribution of free volume holes arising from the incorporation of the branched structure. © 2013 Society of Chemical Industry     

Emulsifier-free emulsion copolymerization of styrene with two different amino-containing monomers: II. Surface and colloidal characterization

The colloidal and surface properties of copolymer latex particles prepared by batch emulsifier-free emulsion polymerization of styrene with two different amino-containing monomers (Amino Ethyl Methacrylate Hydrochloride (AEMH) and Vinyl Benzyl Amine Hydrochloride (VBAH)), and 2,2′-azobis(2-amidinopropane) dihydrochloride (V50) as initiator were investigated. The final particle size was found to decrease with increasing the functional monomer concentration. Different titration methods were used to quantify the surface amino (brought by the monomer) and amidino groups (originated from the initiator) on the latex particles. The same behavior was observed on both type of latexes: increasing the functional monomer concentration caused the surface amino groups density to increase from 0 to a plateau value at 8.2 μC/cm², whereas the surface amidino groups density decreased from 18.5 to 2 μC/cm². These results were confirmed by electrophoretic measurements and they corroborated those obtained in a previous kinetic study (Part 1) concerning the role of functional monomers as transfer agents. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2331–2342, 1997     

RAFT polymerization and thiol-ene modification of 2-vinyloxyethyl methacrylate: Towards functional branched polymers

A vinyl functional polymer, viz, poly(vinyloxyethyl methacrylate) (poly(VEMA) was synthesized by the RAFT polymerization of an asymmetric divinyl monomer, VEMA. This polymer, with pendant vinyloxyl groups, was subsequently reacted with three thiol compounds; 2-mercaptoethanol, cysteamine and 3-mercaptoproponic acid via the thiol-ene reactions. The resulting branched polymers contained hydroxyl, amino and carboxylic acid functionalities suitable for further reactions and conjugations.     

Concept of quasimonomers and its application to some problems of polymer statistics

The concept of quasimonomers is introduced, i.e. the concept of disconnected quasiparticles, which can be effectively substituted for a chain of connected monomers in the analysis of volume interactions in polymeric coils. Such a substitution becomes possible because each monomer of an infinite homogeneous chain is ‘standardly surrounded’ by the other monomers (primarily by near neighbours along the chain) and solvent molecules. This ‘standard surrounding’ renormalizes the monomer characteristics in such a way that each monomer can be considered as a disconnected quasiparticle, the properties of which do not coincide with the properties of the initial monomer. The application of the concept of quasimonomers to the analysis of volume interactions in inhomogeneous macromolecules (finite linear macromolecules, macromolecules with defects and branched macromolecules) leads to results which differ from the results of classical Flory-type theories. This is connected with the fact that the interaction characteristics for these macromolecules turn out to be dependent on the positions of corresponding monomers in the chain. The following topics are considered with the help of the method of quasimonomers: the θ behaviour of finite chains, of chains with defects and of branched chains; the partial specific volume of polymeric macromolecules; and the relation between the polymer chain models. In Appendix 2 the good solvent behaviour of branched macromolecules is also discussed.     

Regioselective introduction of β-galactoside branches into chitosan and chitin

β-d-Galactoside branches have been introduced into chitosan and chitin regioselectively through a series of controlled modification reactions based on N-phthaloyl-chitosan. The glycosylation reaction between a chitosan derivative having a reactive group only at C-6 and an orthoester of d-galactose proceeded efficiently to give a protected product with a degree of substitution up to about 0.5. Deprotection gave a branched chitosan, and the subsequent N-acetylation afforded a branched chitin. Unlike chitosan and chitin, the resulting nonnatural branched polysaccharides were characterized by high affinity for solvents and readily soluble in neutral water. Furthermore, branched chitin was easily degraded by lysozyme. Received: 31 July 1997/Revised: 2 September 1997/Accepted: 19 September 1997     

Preparation of acid-cleavable branched polymers for argon fluoride photoresists via reversible addition–fragmentation chain-transfer polymerization

A series of branched polymers for chemically amplified resists (CARs) were prepared through the reversible addition–fragmentation chain-transfer (RAFT) copolymerization of three monomers with lithographic functionalities and an acid-cleavable dimethacrylate monomer. The three monomers with lithographic functionalities were 2-ethyl-2-adamantyl methacrylate, α-γ-butyrolactone methacrylate, and 3-hydroxy-1-adamantyl methacrylate. The acid-cleavable monomer was 2,5-dimethyl-2,5-hexanediol dimethacrylate (DMHDMA), and 2-cyanoprop-2-yl-1-dithionaphthalate was used as a chain-transfer agent. Because DMHDMA contains two methacrylate groups, it induced the branched structures of the polymers. The degree of branching could be controlled by the molar fraction of DMHDMA in the monomer mixtures. The size and structure of the polymers obtained after hydrolysis were very close to those of linear polymers prepared by RAFT copolymerization with the same amount of reagents, only without the acid-cleavable monomer. A preliminary lithography test using an argon fluoride source demonstrated that the acid-cleavable branched polymers could be promising candidates for CAR materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Fabrication of thin-film composite membranes with pendant,photoreactive diazoketone functionality

A disulfonyl chloride monomer having a pendent photoreactive diazoketone functional group has been synthesized in high overall yield (>90%). The synthesis involves a convenient two-step reaction sequence starting from commercially available 6-diazo-5-oxo-5,6-dihydro-1-naphthalenesulfonyl chloride, which was reacted with piperazine then 1,3,6-naphthalenetrisulfonyl chloride to give the disulfonyl chloride diazoketone. Thin-film composite membranes having photoreactive diazoketone moieties as side chains of a polysulfonamide have been successfully fabricated by interfacial polymerization of ethanediamine with the disulfonyl chloride diazoketone on a polysulfone support. The effect of polymerization parameters such as monomer concentration, polymerization time, crosslinking, and surfactant have been systematically investigated in terms of membrane morphology and permeation properties. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2381–2398, 1997     

Studies on the development of branching in ATRP of styrene and acrylonitrile in the presence of divinylbenzene

Branching atom transfer radical polymerization (ATRP) of styrene and acrylonitrile was attempted in the presence of divinylbenzene targeting toward soluble branched copolymer. The kinetics and the development of branching with monomer conversion were studied in detail. Gas chromatography (GC), gel permeation chromatography (GPC) coupled with multi-angle laser light scattering (MALLS), proton nuclear magnetic resonance (¹H NMR) spectroscopy and intrinsic viscosity determination were used to monitor the polymerization process and characterize the obtained copolymer. Analysis of conversion of reactants, the growth manner of molecular weight with monomer conversion and GPC traces proved that the primary chains with low polydispersity formed mainly at the early stage and then were linked in a statistical manner to start the branching at the middle or late stage. The more the branching agent was used, the earlier the branching occurred, and too much higher level of branching agent resulted in gelation. For the selected ratio of [t-BBiB]/[DVB]/[St]/[AN] = 1/0.9/15/15, with monomer conversion less than 40%, primary chains with low polydispersity formed from the polymerization of St, AN and DVB, and only a part of the primary chains contained pendent vinyl group. When monomer conversion was up to 40%, the pendent vinyl groups participated in polymerization, resulting in the linking of the primary chains statistically to start the branching. The branching became significant at monomer conversion up to 50%, giving rise to a steep increase in molecular weight and width in molecular weight distribution. As the polymerization proceeded, the polymer composition gradually approached the feed composition, identifying the obtained branched copolymer provided some gradients are in its primary chains. Finally, branched copolymer bearing about six primary chains was prepared at monomer conversion near to 80%, its absolute weight average molecular weight was about 8.87 × 10⁴.     

Spontaneous copolymerization of N-(2-hydroxyethyl)ethyleneimine with isatoic anhydride

The polymerization of isatoic anhydride (electrophilic monomer) with N-(2-hydroxyethyl)ethyleneimine (nucleophilic monomer) was studied in the absence of added initiator at different feed monomer concentrations, temperature, and time of copolymerization. The copolymers were characterized by FT-IR, ¹H-NMR and ¹³C-NMR spectroscopy, and TGA. Based on spectroscopic data and copolymer composition, a copolymer structure was suggested. Received: 25 April 1997/Revised: 11 August 1997/Accepted: 14 August 1997     

Combining control of branching and sulfonation in one-pot synthesis of random sulfonated polyarylethersulfones: effects on thermal stability and water retention

In functional polymers with tunable hydrophilic behaviour like sulfonated polyarylethersulfone (SPES) high ionic conductance can be obtained directly by increasing the concentration of sulfonic moieties along the macromolecular chain. This, however, often comes to the cost of excessive water sorption, which can lead to membrane rupture and consequent device failure. To overcome this drawback, and to reconcile high hydrophilicity with the high mechanical properties of aromatic polymers, we propose the use of SPES copolymers with a low degree of branching. A series of branched SPES was synthesized using homogeneous (one-pot) copolymerization by replacing an amount up to 0.9% mol of the difunctional monomer 4,4′-dihydroxydiphenyl with the trifunctional 1,3,5-trihydroxybenzene (THB). The polymers were characterized by ¹H-NMR spectroscopy, intrinsic viscosity, water sorption measurements, thermogravimetric analysis and differential scanning calorimetry. Like linear SPES, branched SPES is totally amorphous and soluble in polar aprotic solvents, lending itself to easy fabrication of membranes and coatings. Besides reducing the water sorption and in-plane swelling of SPES membranes upon equilibration in liquid, branching also improves the retention of water in swollen membranes.     

Structure and properties of blends of poly(ethylene-co-vinyl alcohol) with poly(styrene-co-maleic anhydride)

In the present study, ethylene/vinyl alcohol (EVAL) copolymers with different hydroxyl contents were melt mixed with styrene/maleic anhydride (SMA) copolymers. These two copolymers have functional groups capable of reacting intermolecularly, giving stable products. All EVAL copolymers were prepared from the same ethylene/vinyl acetate (EVA) copolymer by controlled hydrolysis. The blends, prepared at constant temperature and rotation speed in the rheomixer, were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermo-gravimetric analysis, as well as mechanical properties and extraction experiments. All the above measurements lead to the conclusion that a certain part of hydroxyls of EVAL have reacted with anhydride groups of SMA, leading to the formation of branched and cross-linked products. The effect of (1) the molar ratio of hydroxyl/maleic anhydride functional groups, (2) the overall concentration of the functional groups, and (3) the mixing time on the structure and properties of the blends are discussed. Emphasis is given on the influence of these factors on the tensile strength, the elongation at break, and impact strength of the products. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 983–999, 1997     

A novel side chain liquid crystalline polyester for nonlinear optics

A nematic liquid crystalline polymalonate has been synthesized by melt polycondensation of a nonlinear optical (NLO) monomer and a liquid crystalline (LC) monomer. The polymer was characterized by VPO, FTIR, DSC, WAXD, UV-visible spectroscopy and polarized optical microscopy. The LC temperature interval was found between 398 K and 420 K by DSC. Some interactions originated from the attachment of the side groups to the polymer backbone were detected by UV-vis spectroscopy. Received: 2 May 1997/Revised 24 June 1997/Accepted: 27 June 1997     

Design,synthesis and polymerization of highly branched pseudodendrimers through tandem reactions

BACKGROUND: Pseudodendrimers are hyperbranched polymers which are isomeric with dendrimers, that is, each repeat unit is either fully reacted or only singly reacted. The careful design of an ABB′ monomer leads to higher branching by virtue of tandem reactions that increase the reactivity of linear units during polymerization, leading to fully reacted repeat units. The resulting polymers are predicted to be very highly branched, and in the optimum case, pseudodendrimers. RESULTS: Our work shows that 6‐amino‐3‐bromophthalide leads to a highly branched polymer via bromohydrin decomposition during polymerization, giving polymers of M? = of 3000 and a polydispersity index of 1.03. Our findings indicate a degree of branching of 0.84. The synthesis of similar polymers using different techniques confirms our proposed intermediate. CONCLUSION: We have demonstrated a new class of hyperbranched polymers which are highly branched, and may be considered pseudodendrimers. Copyright © 2009 Society of Chemical Industry     

The in-situ synthesis of protective coatings on steel through a surface spontaneous polymerization process

This article reports a new method of forming protective coatings on metal surfaces. The process is very simple and environmentally friendly. Polymerization occurs spontaneously on the metal surface after the immersion of a cleaned metal substrate into a dominantly aqueous monomer solution. A layer of coating with uniform thickness is formed in situ. The coating thickness can be controlled from 1 to 50 μm. This article will describe the spontaneous polymerization process as it occurs specifically on steel and for a 4-carboxyphenyl maleimide—styrene monomer system. The polymerization propagation mechanism is free radical, and alternating copolymers are always obtained in this system, even with significant changes in the monomer feed composition. This could be attributed to the formation of a charge transfer complex between the monomer pair. The incorporation of the rigid imide ring into the copolymer backbone significantly improves the coating's thermal properties, and styrene enhances the electrical properties. These properties are relatively insensitive to the monomer feed composition, supporting the formation of alternating copolymer. The effects of several process variables have been evaluated, including solution pH, monomer concentration, solution temperature, and monomer feed composition. The proposed initiation mechanism involves the direct electrochemical reduction of the monomer by the steel surface to generate the initiating free radicals. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1667–1680, 1997     

Hyperbranched poly(methyl methacrylate)s prepared by miniemulsion polymerization and their (non)-Newtonian flow behaviors

Miniemulsion polymerization is most suitable for the targeted synthesis of vinyl copolymers than the conventional emulsion polymerization, because in miniemulsion polymerization each monomer nanodroplet is a nanoreactor, and the monomers in each droplet are in situ converted to the corresponding polymers. Soluble and hyperbranched poly(methyl methacrylate)s (PMMA) were prepared with quantitative monomer conversion and without gelation by the miniemulsion copolymerization with di- and tri-acrylate and mediated with 1-dodecyl thiol (DDT). DDT acted both as a gelation prohibitor and as a reactive cosurfactant. The PMMAs with varied “X” or “Ж” shaped branches, depending on the di- and tri-functional acrylate used as the branching agent, are characterized and interpreted in terms of the repeating units per part, parts and branches per macromolecule, average molecular weight, latex particle size and size distribution. Effects of topology changes of the branched PMMAs on the rheological behaviors are observed for the first time: from Newtonian flow for the densely branched PMMAs to the non-Newtonian flow with pronounced shear thickening for the PMMA samples with high-molecular-weight and longer parts.     

Flame retardant polypropylene fibers with good dyeability

Polypropylene has been grafted with pentabromobenzyl acrylate by reactive extrusion. The degree of grafting is about 4% by weight of the polypropylene independent of the weight of brominated monomer in the feed. Ungrafted monomer remains largely unreacted. Fibers spun from the grafted polypropylene display good mechanical properties and are easily dyed with anthraquinone type disperse dyes. The dyed cloths have good color stability even after laundering. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 601–606, 1997     

Thermal and mechanical properties of tetra‐functional mesogenic type epoxy resin cured with aromatic amine

A novel tetra‐functional epoxy monomer with mesogenic groups was synthesized and characterized by ¹H‐NMR and FTIR. The synthesized epoxy monomer was cured with aromatic amine to improve the thermal property of epoxy/amine cured system. The glass transition temperature (T_g) and coefficient of thermal expansion (CTE) of the cured system were investigated by dynamic mechanical analysis and thermal mechanical analysis. The properties of the cured system were compared with the conventional bisphenol‐A type epoxy and mesogenic type epoxy system. The storage modulus of the tetra‐functional mesogenic epoxy cured systems showed the value of 0.96 GPa at 250 °C, and T_g‐less behavior was clearly observed. The cured system also showed a low CTE at temperatures above 150 °C without incorporation of inorganic components. These phenomena were achieved by suppression of the thermal motion of network chains by introduction of both mesogenic groups and branched structure to increase the cross linking density. The temperature dependency of the tensile property and thermal conductivity of the cured system was also investigated. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46181.