Synthesis of Novel Core Cross‐Linked Star‐Based Polyrotaxane End‐Capped via “CuAAC” Click Chemistry

The first example of core cross‐linked star (CCS) polyrotaxane was prepared using the poly(ϵ‐caprolactone) (PCL) CCS three‐dimensional (3D) scaffold. The 3D CCS polymer was firstly prepared through the “arm‐first” approach. Then, the “arms” of the resultant PCL CCS polymer were threaded with α‐cyclodextrins (α‐CDs). The threaded α‐CDs were permanently locked by the “click” reaction of terminal alkyne functionalities of the star polymers with the azide‐functionalized end caps to afford the CCS polyrotaxanes. All analytical results confirm the formation of the CCS polyrotaxanes and reveal their characteristics, including fluorescence under UV, a channel‐type crystalline structure, a two‐step thermal decomposition, and a unique core‐shell structure in great contrast to the polymer precursors.     

Phase separation kinetics in unentangled polymer solutions under high‐rate extension

Phase separation processes following high‐rate extension in unentangled polymer solutions are studied theoretically. The flow‐induced demixing is associated with the coil–stretch transition predicted in high‐molecular‐weight polymer solutions at high‐enough Weissenberg numbers. The developed mean‐field theory is valid in the dilute/semidilute solution regime, where the stretched coils overlap strongly. We elucidate and discuss the main kinetic stages of the polymer/solvent separation process including (i) growth of concentration fluctuations and formation of oriented protofibrils by anisotropic spinodal decomposition; (ii) development of well‐defined highly oriented and stiff fibrils forming an anisotropic network (cross‐linked fiber); (iii) microphase separation and lateral collapse of the network yielding dense oriented fiber. These novel predictions are in qualitative agreement with the experimental data. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 623–637     

A Density Functional Theory (DFT) Quantum‐Chemical Approach to the Real Structure of Poly(methylaluminoxane)

DFT quantum chemical calculations have been performed in order to optimize the geometric and electronic cage structure of poly(methylaluminoxane) (MAO) with oligomerization degree n = 9–15, and to find such structures that fit most closely the existing experimental data on the MAO composition and structure. The following peculiarities of the MAO structure were found: i) In “classic” MAO (n = 9, 12, 15; Al : CH₃ : O = 1 : 1 : 1), which has a triple‐layer cage structure, the inner layer contains highly reactive Al‐O bonds. ii) The reaction between “classic MAO” and trimethylaluminium (TMA) proceeds by the concerted mechanism, with the insertion of Al‐CH₃ groups into these Al‐O bonds producing “true” MAO (Al : CH₃ : O = 1 : 1.5 : 0.75). The calculated geometric and electronic structures of “true” MAO with n = 6, 9, 12 are presented. iii) “True” MAO and “classic” MAO exist in equilibrium. The driving force for the formation of “true” MAO is the decrease in enthalpy, and of “classic” MAO the increase in entropy, in the equilibrium reaction between “classic” MAO and TMA.     

One‐pot synthesis of surface‐functionalized molecularly imprinted polymer microspheres by iniferter‐induced “living” radical precipitation polymerization

This article describes for the first time the development of a new polymerization technique by introducing iniferter‐induced “living” radical polymerization mechanism into precipitation polymerization and its application in the molecular imprinting field. The resulting iniferter‐induced “living” radical precipitation polymerization (ILRPP) has proven to be an effective approach for generating not only narrow disperse poly(ethylene glycol dimethacrylate) microspheres but also molecularly imprinted polymer (MIP) microspheres with obvious molecular imprinting effects towards the template (a herbicide 2,4‐dichlorophenoxyacetic acid (2,4‐D)), rather fast template rebinding kinetics, and appreciable selectivity over structurally related compounds. The binding association constant K_a and apparent maximum number N_max for the high‐affinity sites of the 2,4‐D imprinted polymer were determined by Scatchard analysis and found to be 1.18 × 10⁴ M^?1 and 4.37 μmol/g, respectively. In addition, the general applicability of ILRPP in molecular imprinting was also confirmed by the successful preparation of MIP microspheres with another template (2‐chloromandelic acid). In particular, the living nature of ILRPP makes it highly useful for the facile one‐pot synthesis of functional polymer/MIP microspheres with surface‐bound iniferter groups, which allows their direct controlled surface modification via surface‐initiated iniferter polymerization and is thus of great potential in preparing advanced polymer/MIP materials. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3217–3228, 2010     

Filler effect on properties of “All‐Acrylic” copolymer/clay elastomeric materials synthesized by “in situ” nitroxide mediated polymerization

In this work, we describe the “in situ” synthesis of “all‐acrylic” copolymer (n‐butyl acrylate‐co‐methyl methacrylate)/clay materials at different low contents of raw and modified Montmorillonite (1–4 wt % versus monomer). The cationic 2,2′ azobis‐(amidinopropane)dihydrochloride initiator was used to modified the clay by cation exchange in combination with the N‐tert‐butyl‐N‐[1‐diethylphosphono‐(2,2‐dimethylpropyl)] (SG1) nitroxide to synthesize the polymer/clay nanocomposite via nitroxide mediated controlled radical polymerization. All synthesized materials are characterized by proton nuclear magnetic resonance, size exclusion chromatography, thermogravimetric analysis and differential scanning calorimetry techniques. The thermo‐mechanical properties of the synthesized materials are also reported. The results show that a decrease in molar masses and/or slight changes in molar compositions of poly (n‐butyl acrylate‐ co‐methyl methacrylate)/clay systems can be balanced by clay loading in polymer matrix, and consequently compensated or masked clay effects on physical properties of obtained materials. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

A Self‐Reporting Photocatalyst for Online Fluorescence Monitoring of High Throughput RAFT Polymerization

Translating controlled/living radical polymerization (CLRP) from batch to the high throughput production of polymer libraries presents several challenges in terms of both polymer synthesis and characterization. Although recently there have been significant advances in the field of low volume, high throughput CLRP, techniques able to simultaneously monitor multiple polymerizations in an “online” manner have not yet been developed. Here, we report our discovery that 5,10,15,20‐tetraphenyl‐21H,23H‐porphine zinc (ZnTPP) is a self‐reporting photocatalyst that can mediate PET‐RAFT polymerization as well as report on monomer conversion via changes in its fluorescence properties. This enables the use of a microplate reader to conduct high throughput “online” monitoring of PET‐RAFT polymerizations performed directly in 384‐well, low volume microtiter plates.     

A New Chiral Binaphthalene‐Based Fluorescence Polymer Sensor for the Highly Enantioselective Recognition of Phenylalaninol

A new (S)‐binaphthalene‐based polymer ( P ‐ 1 ) was synthesized by the polymerization of 5,5′‐((2,5‐dibutoxy‐1,4‐phenylene)bis(ethyne‐2,1‐diyl))bis(2‐hydroxy‐3‐(piperidin‐1‐ylmethyl) benzaldehyde ( M ‐ 1 ) with (S)‐2,2′‐dimethoxy‐(1,1′‐binaphthalene)‐3,3′‐diamine ( M ‐ 2 ) through the formation of a Schiff base; the corresponding chiral polymer ( P ‐ 2 ) could be obtained by the reduction of polymer P ‐ 1 with NaBH₄. Chiral polymer P ‐ 1 exhibited a remarkable “turn‐on” fluorescence‐enhancement response towards (D )‐phenylalaninol and excellent enantioselective recognition behavior with enantiomeric fluorescence difference ratios (ef) as high as 8.99. More importantly, chiral polymer P ‐ 1 displays a bright blue fluorescence color change upon the addition of (D )‐phenylalaninol under a commercially available UV lamp, which can be clearly observed by the naked eye. On the contrary, chiral polymer P ‐ 2 showed weaker enantioselective fluorescence ability towards the enantiomers of phenylalaninol.     

Isoindigo‐3,4‐Difluorothiophene Polymer Acceptors Yield “All‐Polymer” Bulk‐Heterojunction Solar Cells with over 7 % Efficiency

Poly(isoindigo‐alt‐3,4‐difluorothiophene) (PIID[2F]T) analogues used as “polymer acceptors” in bulk‐heterojunction (BHJ) solar cells achieve >7 % efficiency when used in conjunction with the polymer donor PBFTAZ (model system; copolymer of benzo[1,2‐b:4,5‐b′]dithiophene and 5,6‐difluorobenzotriazole). Considering that most efficient polymer‐acceptor alternatives to fullerenes (e.g. PC₆₁BM or its C₇₁ derivative) are based on perylenediimide or naphthalenediimide motifs thus far, branched alkyl‐substituted PIID[2F]T polymers are particularly promising non‐fullerene candidates for “all‐polymer” BHJ solar cells.     

Preparation of molecularly imprinted polymers via atom transfer radical “bulk” polymerization

The first application of atom transfer radical “bulk” polymerization (ATRBP) in molecular imprinting is described, which provides molecularly imprinted polymers (MIPs) with obvious imprinting effects towards the template, very fast binding kinetics, and an appreciable selectivity over structurally related compounds. In comparison with the MIP prepared via the normally used traditional “bulk” free radical polymerization (BFRP), the MIPs obtained via ATRBP showed somewhat lower binding capacities and apparent maximum numbers N_max for high‐affinity sites as well as quite similar binding association constants K_a for high‐affinity sites and high‐affinity site densities, in contrast with the previous reports (e.g., nitroxide/iniferter‐mediated “bulk” polymerization provided MIPs with improved properties). This is tentatively ascribed to the occurrence of rather fast gelation process in ATRBP, which greatly restricted the mobility of the chemical species, leading to a heavily interrupted equilibrium between dormant species and active radicals and heterogeneous polymer networks. In addition, the general applicability of ATRBP was also confirmed by preparing MIPs for different templates. This work clearly demonstrates that applying controlled radical polymerizations (CRPs) in molecular imprinting not always benefits the binding properties of the resultant MIPs, which is of significant importance for the rational use of CRPs in generating MIPs with improved properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 532–541, 2010     

Intrinsically Porous Polymer Protects Catalytic Gold Particles for Enzymeless Glucose Oxidation

The enzymeless glucose oxidation process readily occurs on nano‐gold electrocatalyst at pH 7, but it is highly susceptible to poisoning (competitive binding), for example from protein or chloride. Is it shown here that gold nanoparticle catalyst can be protected against poisoning by a polymer of intrinsic microporosity (PIM‐EA‐TB with BET surface area 1027 m² g^?1). This PIM material when protonated, achieves a triple catalyst protection effect by (i) size selective repulsion of larger protein molecules (albumins) and (ii) membrane ion selection effects, and (iii) membrane ion activity effects. PIM materials allow “environmental control” to be introduced in electrocatalytic processes.     

A Monte Carlo study of a tethered polymer chain in a uniform field

We study the non‐uniform stretching and relaxation of a long flexible end‐anchored polymer chain of N monomers (32 ≤ N ≤ 1 024) in a uniform field B by means of an off‐lattice bead‐spring Monte Carlo model. Our simulational results for the case of a Rouse‐like polymer in the good solvent regime confirm the existence of “trumpet”‐ and “flower”‐type chain conformations, predicted recently by scaling analysis based on the notion of Pincus tensile blobs. The observed elongation of the chain and the critical fields, separating three different regimes of chain deformation, are found to obey the predicted scaling behavior. The segment density distribution matches that of a DNA molecule pulled from one end at constant velocity in a good solvent. As expected, the relaxation of the stretch to coil transition of the polymer of length N is determined by the typical Rouse time τ ∝ N^2ν+1.     

Facile one‐pot/one‐step technique for preparation of side‐chain functionalized polymers: Combination of SET‐RAFT polymerization of azide vinyl monomer and click chemistry

An azido‐containing functional monomer, 11‐azido‐undecanoyl methacrylate, was successfully polymerized via ambient temperature single electron transfer initiation and propagation through the reversible addition–fragmentation chain transfer (SET‐RAFT) method. The polymerization behavior possessed the characteristics of “living”/controlled radical polymerization. The kinetic plot was first order, and the molecular weight of the polymer increased linearly with the monomer conversion while keeping the relatively narrow molecular weight distribution (M_w/M_n ≤ 1.22). The complete retention of azido group of the resulting polymer was confirmed by ¹H NMR and FTIR analysis. Retention of chain functionality was confirmed by chain extension with methyl methacrylate to yield a diblock copolymer. Furthermore, the side‐chain functionalized polymer could be prepared by one‐pot/one‐step technique, which is combination of SET‐RAFT and “click chemistry” methods. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Polystyrene microspheres having epoxy functional dangling chains linked by hydrolytically stable bonds via ATRP

We report application of copper‐mediated atom transfer radical polymerization in graft copolymerization of glycidyl methacrylate (GMA) from N‐bromosulfonamide groups on polystyrene‐divinyl benzene (PS‐DVB) microspheres (210–420 μm). The surface initiator groups were introduced by simple modification of crosslinked PS‐DVB (10% mol/mol) beads in three steps: (i) chlorosulfonation, (ii) sulfamidation with propylamine, and (iii) bromination. Initiation from surface‐bound N‐bromosulfonamide groups showed first‐order kinetics (k = 1.04 × 10^?4 s^?1 in toluene at 70 °C) and gave poly(GMA) graft chains linked to the surface by hydrolytically stable sulfonamide bonds. High graft yields were attained (up to 294.4% within 21 h) while retaining the epoxy groups. Epoxy content of the resulting product (5.41 mmol g^?1) revealed an average 17 GMA repeating units in the graft per initiation site. Taking advantage of the hydrolytic stability of sulfonamide linkages and well‐known reactivity of the epoxy groups on dangling chains, “the hair‐like structure” of the polymer beads prepared can be considered when devising more efficient functional polymers as catalysts or reagent carriers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6708–6716, 2006     

Synthesis and characterization of polymer linked copper(I) bis(N‐heterocyclic carbene) mechanocatalysts

In this paper, the synthesis and characterization of a series of latent polymeric bis(N‐heterocyclic carbene) (NHC) copper(I) complexes is reported, which can be activated for the copper(I)‐catalyzed azide/alkyne cycloaddition (CuAAC) via ultrasound. To prove the influence of chain length and nature of the polymer towards the activation, poly(isobutylene) (PIB), poly(styrene) (PS) and poly(tetrahydrofuran) (PTHF) are synthesized via living polymerization techniques (LCCP, ATRP, CROP) obtaining different chain lengths (from 2500 to 9000 g/mol), followed by quaternization with N‐methylimidazole, generating the corresponding N‐methylimidazolium‐telechelic polymers. The deprotonation of these macroligands via strong bases like sodium tert‐butoxide (NaO^tBu) or potassium hexamethyldisilazide (KHMDS) yields the free N‐heterocyclic carbenes (NHCs), which are used to coordinate to tetrakis(acetonitrile)copper(I) hexafluorophosphate, forming the final polymer‐based mono‐ and bis(N‐methylimidazole‐2‐ylidene) copper(I)X complexes. The structural proof of these complexes is accomplished via ¹H‐NMR spectroscopy, MALDI‐TOF‐MS and GPC‐techniques. The activation of the copper(I) biscarbene catalysts by ultrasound is studied by GPC, revealing the cleavage of one shielding NHC‐ligand. The initial catalytic latency and the via ultrasound introduced catalytic activation is successfully demonstrated monitoring a CuAAC “click” reaction of benzyl azide and phenylacetylene by in situ ¹H‐NMR spectroscopy introducing thus “click” conversions up to 97%. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3893–3907     

Synthesis and functionalization of dendron‐polymer conjugate based hydrogels via sequential thiol‐ene “click” reactions

Fabrication and functionalization of hydrogels from well‐defined dendron‐polymer‐dendron conjugates is accomplished using sequential radical thiol‐ene “click” reactions. The dendron‐polymer conjugates were synthesized using an azide‐alkyne “click” reaction of alkene‐containing polyester dendrons bearing an alkyne group at their focal point with linear poly(ethylene glycol)‐bisazides. Thiol‐ene “click” reaction was used for crosslinking these alkene functionalized dendron‐polymer conjugates using a tetrathiol‐based crosslinker to provide clear and transparent hydrogels. Hydrogels with residual alkene groups at crosslinking sites were obtained by tuning the alkene‐thiol stoichiometry. The residual alkene groups allow efficient postfunctionalization of these hydrogel matrices with thiol‐containing molecules via a subsequent radical thiol‐ene reaction. The photochemical nature of radical thiol‐ene reaction was exploited to fabricate micropatterned hydrogels. Tunability of functionalization of these hydrogels, by varying dendron generation and polymer chain length was demonstrated by conjugation of a thiol‐containing fluorescent dye. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 926–934     

Designed organo‐layered silicates as nanoreactors for 1,3‐butadiene stereospecific polymerization toward rubber nanocomposites synthesis

Organo‐modified layered silicates were synthesized and used as inorganic carriers for CoCl₂(P^tBu₂Me)₂‐MAO catalyst in the polymerization of 1,3‐butadiene, yielding cis‐1,4‐enriched polybutadiene. The organoclays were prepared by: (i) intercalation of (ar‐vinyl‐benzyl)trimethyl ammonium chloride salt through an ion exchange reaction, and (ii) the edge‐surface grafting by trimethylchlorosilane. The ammonium modifier acts as “spacer” increasing the layer d‐spacing and as “filler” favoring the silylation of the edge‐surface clay hydroxyls. The grafted silane prevents the MAO cocatalyst from reacting with the edge‐OHs, by forcing it to react within the interlayer clay region. MAO lead to methylation of the cobalt complex and carbanion abstraction to give a cobalt‐methyl cation that is stabilized by the MAO anion. The nanoconfined cationic alkylated species insert the butadiene on the Co‐Me bond affording the growth of the polymer chains within the clay layers. The growing of the macromolecular chains fills the interlayer silicate region giving an intercalated polybutadiene rubber nanocomposite. The role of the silicate organo modification on the heterogeneous catalyst structural features, the polymerization behavior and the nanocomposite structures are discussed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Microstructure of Highly Syndiotactic “Living” Poly(propylene)s Produced from a Titanium Complex with Chelating Fluorine‐Containing Phenoxyimine Ligands (an FI Catalyst)

Highly syndiotactic “living” poly(propylene)s were synthesized at 25°C using a bis[N‐(3‐tert‐butylsalicylidene)‐2,3,4,5,6‐pentafluoroanilinato]titanium (IV) dichloride/MAO catalyst system, and microstructures of the polymer were analyzed by means of ¹³C NMR spectroscopy. The syndiotactic poly(propylene) contains isobutyl, isopentyl and propyl end groups, suggesting that the living polymerization of propylene was initiated via 1,2‐insertion, followed by 2,1‐insertion as the principal mode of polymerization. Pentad distribution analysis revealed that the syndiospecific polymerization proceeds under chain‐end control.     

A helical chiral polymer‐based chromo‐fluorescence and CD response sensor for selective detection of trivalent cations

A novel chiral (S)‐BINAM‐based fluorescent polymer sensor was designed and synthesized by the polymerization of 4,4′‐((2,5‐dibutoxy‐1,4‐phenylene)bis(ethyne‐2,1‐diyl))‐dibenzaldehyde ( M‐1 ) with (S)‐2,2′‐binaphthyldiamine (S‐BINAM, M‐2 ) via Schiff's base formation. The resulting helical chiral polymer sensor exhibited remarkable “turn‐on” bright blue fluorescence color upon the addition of trivalent metal ions under a commercially available UV lamp; this change can be clearly observed by the naked eye for direct visual discrimination at low concentration. More importantly, the addition of trivalent metal cations can lead to a most pronounced change of CD spectra of the chiral polymer indicating this kind chiral sensor can also be used as a sole probe for selective recognition of trivalent metal cations based on CD spectra. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4070–4075     

Polyimide polydimethylsiloxane triblock copolymers for thin film composite gas separation membranes

This article demonstrates the successful fabrication of thin‐film‐composite (TFC) membranes containing well‐defined soft‐hard‐soft triblock copolymers. Based on “hard” polyimide (PI) and “soft” polydimethylsiloxane (PDMS), these triblock copolymers (PDMS‐b‐PI‐b‐PDMS), were prepared via condensation polymerization, and end‐group allylic functionalization to prepare the polyimide component and subsequent “click” coupling with the soft azido functionalized PDMS component. The selective layer consisted of pure PDMS‐b‐PI‐b‐PDMS copolymers which were cast onto a precast crosslinked‐PDMS gutter layer which in turn was cast onto a porous polyacrylonitrile coated substrate. The TFC membranes' gas transport properties, primarily for the separation of carbon dioxide (CO₂) from nitrogen (N₂), were determined at 35 °C and at a feed pressure of 2 atm. The TFC membranes showed improvements in gas permselectivity with increasing PDMS weight fraction. These results demonstrate the ability for glassy, hard polymer components to be coated onto otherwise incompatible surfaces of highly permeable soft TFC substrates through covalent coupling. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3372–3382