Photo-induced Living Cationic Copolymerization of Isobutyl Vinyl Ether and Vinyl Ether with Carbazolyl Groups

In this work, a fluorescent monomer 2-（9-carbazolyl） ethyl vinyl ether（CEVE） was synthesized in our lab, and its photo-induced living cationic copolymerization behavior with isobutyl vinyl ether（IBVE） was investigated in detail using diphenyliodonium chloride（DPICl）/2,2-dimethoxy-2-phenylacetophenone（DMPA） and zinc bromide（Zn Br2） initiating system in dichloromethane solution at 5 °C, -5 °C, and -15 °C, respectively. The living nature of this copolymerization system was confirmed by adding fresh comonomer method after the copolymerization almost finished. In addition, the obtained fluorescent copolymer poly（IBVE-co-CEVE） has a low glass transition temperature（Tg）, below -10 °C.

Real-time Monitoring of Living Cationic Ring-opening Polymerization of THF and Direct Prediction of Equilibrium Molecular Weight of Poly THF

A convenient real-time monitoring of monomer concentration during living cationic ring-opening polymerizations of tetrahydrofuran（THF） initiated with methyl triflate（Me OTf） has been developed for kinetic investigation and determination of equilibrium monomer concentration（[M]e） via in situ FTIR spectroscopy in combination with a diamond tipped attenuated total reflectance（ATR） immersion probe. The polymerization rate was first order with respect to monomer concentration and initiator concentration from the linear slope of ln（[M]0-[M]e）/（[M]-[M]e） versus polymerization time at different temperatures in various solvents. [M]e decreased linearly with initial monomer concentration while increased exponentially with increasing polymerization temperature. The equilibrium also strongly depends on solvent polarity and its interaction with monomer. The equilibrium polymerization time（te） decreased with increasing solvent polarity and decreased linearly with increasing [M]0 in three solvents with different slopes to the same point of bulk polymerization in the absence of solvent. Equation of Mn,e = 72.1/（0.14–0.04[M]e） has been established to provide a simple and effective approach for the prediction for the number-average molecular weight of poly THFs at equilibrium state（Mn,e） in the equilibrium living cationic ring-opening polymerization of THF at 0 °C.

ABA TRIBLOCK COPOLYMERS WITH PENDANT HYDROXYL GROUPS PREPARED BY CONTROLLED CATIONIC POLYMERIZATION AND THEIR USE AS DELIVERY CARRIER FOR PACLITAXEL

To improve the hydrophilicity ofpoly（styrene-b-isobutylene-b-styrene） （SIBS）, this study focuses on the synthesis of novel functional ABA triblock copolymer thermoplastic elastomers （TPEs） with polyisobutylene （PIB） as rubbery segments. The precursor poly{（styrene-co-4-[2-（tert-butyldimethylsiloxy） ethyl]styrene）-b-isobutylene-b-（styrene-co-4-[2- （tert-butyldimethylsiloxy）ethyl]styrene）}（P（St-co-TBDMES）-PIB-P（St-co-TBDMES）） triblock copolymer was first synthesized by living sequential cationic copolymerization of isobutylene （IB） with styrene （St） and 4-[2-（tert- butyldimethylsiloxy）ethyl]styrene （TBDMES） using 1,4-di（2-chloro-2-propyl）benzene （DiCumC1）/titanium tetrachloride （TiCla）/2,6-di-tert-butylpyridine （DtBP） as the initiating system. Then, P（St-co-TBDMES）-PIB-P（St-co-TBDMES） was hydrolyzed in the presence of tetra-butylammonium fluoride to yield poly{[styrene-co-4-（2-hydroxyethyl）styrene]-b- isobutylene-b-[styrene-co-4-（2-hydroxyethyl）styrene]} （P（St-co-HOES）-PIB-P（St-co-HOES）） with pendant hydroxyl groups. P（St-co-HOES）-PIB-P（St-co-HOES） used as the paclitaxel carrier was also investigated in this study. Comparing with SIBS, P（St-co-HOES）-PIB-P（St-co-HOES） has exhibited better compatibility with paclitaxel and higher release rate.

Living Copolymerization of EOVE and MOVE:Fast Flow Synthesis and Thermal Responsive Behavior

Random and block copolymers of 2-methoxyethyl vinyl ether(MOVE)and 2-ethoxyethyl vinyl ether(EOVE)were synthesized within 180 s via IBVE-HCl/SnCl_(4) initiating system in the presence of THF in a microflow system.The polymers can be produced continuously and efficiently with extremely narrow molecular weight distributions(M_(w)/M_(n)=1.09-1.18)even at the existence of pendant oxyethylene units Polymerization rate can be accelerated by reducing THF to very low concentration([THF]=50 mmol/L),reaching conversions over 60%and 70%in 60 s for EOVE and MOVE,respectively.Random copolymers poly(MOVE_(100x)-r-EOVE(_(100)(1-x)))(x=0.25,0.5,0.75)experienced very sensitive phase separation process,of which phase separation temperature(T_(ps))can be adjusted between 20 and 70℃by controlling monomer composition.On the other hand,thermally induced phase separation of diblock copolymers poly(MOVE_(100)-b-EOVE_(100))was not so sensitive as its random copolymer counterpart.Relatively bigger difference between phase separation temperatures of heating and cooling process(ΔT_(ps))was found for diblock copolymer.

Nanocrystallization-locked Network of Poly(styrene-6-isobutylene-6-styrene)-g-Polytetrahydrofuran Block Graft Copolymer

Poly(styrene-6-isobutylene-6-styrene)triblock copolymer(SIBS),a kind of thermoplastic elastomer with biocompatibility and biostability containing fully saturated soft segments,could be synthesized via living cationic copolymerization.A novel poly[(styrene-co-methylstyrene)-b-isobutylene-b-(styrene-co-methylstyrene)]-g-polytetrahydrofuran(M-SIBS-g-PTHF)block graft copolymer was prepared to increase the polarity and service temperature of SIBS by grafting polar PTHF segments onto SIBS.A series of the above block graft copolymers with average grafting numbers from 2 to 6 and molecular weights of PTHF branches ranging from 200 g·mol^(-1)to 4200 g·mol^(-1)were successfully synthesized via living cationic ring-opening polymerization of tetrahydrofuran(THF)coinitiated by AgCI04.The introduction of PTHF branches led to an obvious microphase separation due to thermodynamic incompatibility among the three kinds of segments of polyisobutylene(PIB),polystyrene(PS)and PTHF.Moreover,the microphase separation promotes the rearrangement of PTHF branches to form the nanocrystallization-locked physically cross-linked network after storage at room temperature for 2 months,leading to insolubility of the copolymers even in good solvents.The melting temperature and enthalpy of PTHF nanocrystallization locked in hard domains of M-SIBS-g5-PTHF-1.1k block graft copolymer increased remarkably up to 153℃and 117.0 J·g^(-1)by 23℃and 11.6 J·g^-1(respectively after storage for long time.Storage modulus(G′)is higher than loss modulus(G″)of M-SIBS-g-PTHF block graft copolymer at temperatures ranging from 100℃to 180℃,which is much higher than those of the SIBS triblock copolymer.To the best of our knowledge,this is the first example of high performance M-SIBS-g-PTHF block graft copolymers containing segments of PIB,PS and PTHF with nanocrystallization-locked architecture.

Magnetic responsive polymer nanofiber composites for easy collecting chemical spills

We describe a simple method to prepare magnetic responsive polydivinylbenzene(PDVB)nanofiber composites by precipitated cationic living polymerization in the present of oleic acid capped Fe3O4 nanoparticles(NPs).The Fe3O4 NPs are encapsulated with the PDVB forming dendrites,from which thin nanofibers are grown in the tip-growth mode.The thin nanofibers are interwoven with the thick nanofibers forming robust composite network.The composites are magnetic responsive and highly efficient to gel almost all chemicals.Separation of the gelled chemicals from water becomes easier with a magnet.The performance is promising for magnetic collection of chemical spills.