27 research outputs found
Rod-Like Amphiphile of Diblock Polyisocyanate Leading to Cylindrical Micelle and Spherical Vesicle in Water
The
self-assembling property of an amphiphilic rod–rod diblock
copolymer has been demonstrated using poly(<i>n</i>-hexyl
isocyanate)-<i>block</i>-poly(2,5,8,11-tetraoxatridecyl
isocyanate) (<b>PHIC-</b><i><b>b</b></i><b>-PEOIC</b>) with different degrees of polymerization for the <b>PHIC</b> and <b>PEOIC</b> segments. The critical aggregation
concentrations (CAC) of <b>PHIC-</b><i><b>b</b></i><b>-PEOIC</b> decreased with the increasing fraction of the
hydrophobic <b>PHIC</b> segment. The relation between the hydrodynamic
radius (<i>R</i><sub>h</sub>) and the <b>PHIC</b>/<b>PEOIC</b> ratio differed from that for the radius of gyration
(<i>R</i><sub>g</sub>). The self-assembled <b>PHIC-</b><i><b>b</b></i><b>-PEOIC</b> was stable in
various polymer concentrations. The ρ parameter (<i>R</i><sub>g</sub>/<i>R</i><sub>h</sub>) strongly suggested that
the macromolecular architecture was a cylindrical micelle for <b>PHIC</b><sub><b>13</b></sub><b>-</b><i><b>b</b></i><b>-PEOIC</b><sub><b>41</b></sub> (ρ
= 1.63) and a spherical vesicle for <b>PHIC</b><sub><b>22</b></sub><b>-</b><i><b>b</b></i><b>-PEOIC</b><sub><b>36</b></sub> (ρ = 1.09) and <b>PHIC</b><sub><b>31</b></sub><b>-</b><i><b>b</b></i><b>-PEOIC</b><sub><b>31</b></sub> (ρ = 1.09). Transmission
electron microscope (TEM) images closely agreed with the structures
of the cylindrical micelle and spherical vesicle, which were expected
based on the ρ parameter
Synthesis of High Molecular Weight and End-Functionalized Poly(styrene oxide) by Living Ring-Opening Polymerization of Styrene Oxide Using the Alcohol/Phosphazene Base Initiating System
The ring-opening polymerization (ROP) of styrene oxide (SO) was carried out using 3-phenyl-1-propanol (PPA) as the initiator and a phosphazene base, 1-<i>tert</i>-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phosphoranylidenamino]-2Λ<sup>5</sup>,4Λ<sup>5</sup>-catenadi(phosphazene) (<i>t</i>-Bu-P<sub>4</sub>), as the catalyst at room temperature. The polymerization proceeded in a living manner, which was confirmed by the kinetic and chain extension experiments, to produce the poly(styrene oxide) (PSO) with a controlled molecular weight (5200–21 800 g mol<sup>–1</sup>) and narrow molecular weight distribution (<1.14). The <sup>1</sup>H NMR and MALDI-TOF MS measurements of the obtained PSO clearly indicated the presence of the PPA residue at the chain end. In addition, the <i>t</i>-Bu-P<sub>4</sub>-catalyzed ROP of SO with functional initiators, such as 4-vinylbenzyl alcohol, 5-hexen-1-ol, 6-azide-1-hexanol, and 3-hydroxymethyl-3-methyloxetane, successfully afforded the corresponding end-functionalized PSO with precise molecular control. The <i>t</i>-Bu-P<sub>4</sub>-catalyzed ROP of SO proceeded through the β- and α-scissions as the main and minor ring-opening manners on the basis of the microstructure of the PSOs analyzed by the <sup>13</sup>C NMR measurement, which was clarified in the model reactions corresponding to the initiation and propagation. For the thermal analysis of PSO, the glass transition temperature and 5% weight loss temperature were found to be 34 and 310 °C, respectively
Diphenyl Phosphate as an Efficient Acidic Organocatalyst for Controlled/Living Ring-Opening Polymerization of Trimethylene Carbonates Leading to Block, End-Functionalized, and Macrocyclic Polycarbonates
The ring-opening polymerization (ROP)
of cyclic carbonates with
diphenyl phosphate (DPP) as the organocatalyst and 3-phenyl-1-propanol
(PPA) as the initiator has been studied using trimethylene carbonate
(TMC), 5,5-dimethyl-1,3-dioxan-2-one, 5,5-dibromomethyl-1,3-dioxan-2-one,
5-benzyloxy-1,3-dioxan-2-one, 5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one,
and 5-methyl-5-propargyloxycarbonyl-1,3-dioxan-2-one. All the polymerizations
proceeded without backbiting, decarboxylation, and transesterification
reactions to afford polycarbonates having narrow polydispersity indices.
In addition, 6-azido-1-hexanol, propargyl alcohol, and <i>N</i>-(2-hydroxyethyl)maleimide were used as functional initiators for
the DPP-catalyzed ROP to produce the end-functionalized poly(trimethylene
carbonate)s. For further modification of the azido end-functionlized
polycarbonate, the macrocyclic poly(trimethylene carbonate) was synthesized
by the intramolecular click cyclization of the α-azido, <i>ω-</i>ethynyl poly(trimethylene carbonate). The DPP-catalyzed
ROP was applicable for the block copolymerization of TMC and <i>δ-</i>valerolactone or <i>ε-</i>caprolactone
to afford poly(trimethylene carbonate)-<i>block</i>-poly(δ-valerolactone)
and poly(trimethylene carbonate)-<i>block</i>-poly(ε-caprolactone),
and for that of TMC and l-lactide using DPP coupled with
4-dimethylaminopyridine without quenching to produce poly(trimethylene
carbonate)-<i>block</i>-poly(l-lactide)
B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>‑Catalyzed Group Transfer Polymerization of <i>N,N</i>-Disubstituted Acrylamide Using Hydrosilane: Effect of Hydrosilane and Monomer Structures, Polymerization Mechanism, and Synthesis of α‑End-Functionalized Polyacrylamides
The
tris(pentafluorophenyl)borane- (B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>-) catalyzed group transfer polymerization (GTP) of <i>N,N</i>-disubstituted acrylamide (DAAm) using
a moisture-tolerant hydrosilane (H<i>Si</i>) as part of
the initiator has been intensively investigated in this study. The
screening experiment using various H<i>Si</i>s suggested
that dimethylethylsilane (Me<sub>2</sub>EtSiH) with the least steric
bulkiness was the most appropriate reagent for the polymerization
control. The chemical structure of the DAAms significantly affected
the livingness of the polymerization. For instance, the polymerization
of <i>N,N</i>-diethylacrylamide (DEtAAm)
using Me<sub>2</sub>EtSiH only showed better control over the molecular
weight distribution, while that of <i>N</i>-acryloylmorpholine
(MorAAm) with a more obstructive side group using the same H<i>Si</i> afforded precise control of the molecular weight as well
as its distribution. Given that the entire polymerization was composed
of the monomer activation, the <i>in situ</i> formation
of a silyl ketene aminal as the true initiator by the 1,4-hydrosilylation
of DAAm, and the GTP process, the polymerization mechanism was discussed
in detail for each specific case, e.g., the B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>-catalyzed polymerizations of DEtAAm and MorAAm and
the polymerization of MorAAm using B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> and Me<sub>3</sub>SiNTf<sub>2</sub> as a double catalytic
system. Finally, the convenient α-end-functionalization of poly(<i>N,N</i>-disubstituted acrylamide) (PDAAm) was
achieved by the <i>in situ</i> preparation of functional
silyl ketene aminals through the 1,4-hydrosilylation of functional
methacrylamides, which has no polymerization reactivity in the Lewis
acid-catalyzed GTP, followed by the Me<sub>3</sub>SiNTf<sub>2</sub>-catalyzed GTP of DAAms
Sub-10 nm Scale Nanostructures in Self-Organized Linear Di- and Triblock Copolymers and Miktoarm Star Copolymers Consisting of Maltoheptaose and Polystyrene
The present paper describes the sub-10
nm scale self-assembly of AB-type diblock, ABA-type triblock, and
A<sub>2</sub>B-type miktoarm star copolymers consisting of maltoheptaose
(MH: A block) and polystyrene (PS: B block). These block copolymers
(BCPs) were synthesized through coupling of end-functionalized MH
and PS moieties. Small-angle X-ray scattering and atomic force microscope
investigations indicated self-organized cylindrical and lamellar structures
in the BCP bulks and thin films with domain spacing (<i>d</i>) ranging from 7.65 to 10.6 nm depending on the volume fraction of
MH block (ϕ<sub>MH</sub>), Flory–Huggins interaction
parameter (χ), and degree of polymerization (<i>N</i>). The BCP architecture also governed the morphology of the BCPs,
e.g. the AB-type diblock copolymer (ϕ<sub>MH</sub> = 0.42),
the ABA-type triblock copolymer (ϕ<sub>MH</sub> = 0.40), and
the A<sub>2</sub>B-type miktoarm star copolymer (ϕ<sub>MH</sub> = 0.45) self-organized into cylinder (<i>d</i> = 7.65
nm), lamellar (<i>d</i> = 8.41 nm), and lamellar (<i>d</i> = 9.21 nm) structures, respectively
Colorimetric Detection of Anions in Aqueous Solution Using Poly(phenylacetylene) with Sulfonamide Receptors Activated by Electron Withdrawing Group
A series of sulfonamide-conjugated poly(phenylacetylene)s
with
various electron withdrawing and donating substituents were designed
and synthesized in order to develop a novel colorimetric probe for
anions in water. The UV–vis absorption measurements, which
were performed in an organic solvent to provide fundamental insights
into the anion detection properties of these polymers, clarified that
the colorimetric response ability is highly enhanced by the incorporation
of strong electron withdrawing groups (EWG). Sulfonamide-conjugated
poly(phenylacetylene) with nitro groups, the strongest EWG, was therefore
used for the detection of anions in an aqueous environment. In a solution
containing up to 20% water, the polymer exhibited obvious color changes
to anions including the biologically important carboxylates. On the
basis of the NMR titration analysis, such a colorimetric response
was confirmed to be based on the deprotonation event of the sulfonamide
binding site, which was suggested to be essential for the detection
of aqueous anions
Synthesis of Star- and Figure-Eight-Shaped Polyethers by <i>t</i>‑Bu‑P<sub>4</sub>‑Catalyzed Ring-Opening Polymerization of Butylene Oxide
The synthesis of well-defined four-armed
star-shaped poly(butylene oxide) and figure-eight-shaped poly(butylene
oxide)s (<i>s</i>-PBO and 8-PBO, respectively) with predicted
molecular weights and narrow molecular weight distributions (<i>M</i><sub>w</sub>/<i>M</i><sub>n</sub>s) was achieved
by the <i>t</i>-Bu-P<sub>4</sub>-catalyzed ring-opening
polymerization (ROP) of butylene oxide (BO). The <i>t</i>-Bu-P<sub>4</sub>-catalyzed ROP of BO using 1,2,4,5-benzenetetramethanol
as the initiator produced <i>s</i>-PBOs having number-average
molecular weights (<i>M</i><sub>n,NMR</sub>s) ranging from
ca. 4000 to 12 000 g mol<sup>–1</sup> and narrow <i>M</i><sub>w</sub>/<i>M</i><sub>n</sub>s of <1.03.
Cleavage of the linkage between the initiator residue and PBO arms
in <i>s</i>-PBO provided evidence for the homogeneous growth
of each arm during the polymerization. The synthesis of 8-PBO was
carried out through three reaction steps including (1) the synthesis
of a PBO possessing two azido groups at the chain center ((N<sub>3</sub>)<sub>2</sub>-(PBO)<sub>2</sub>) by the ROP of BO using 2,2-bis((6-azidohexyloxy)methy)propane-1,3-diol
as the initiator, (2) the introduction of an ethynyl group at the
two ω-chain ends by etherification using propargyl bromide to
give the ω,ω′-diethynyl poly(butylene oxide) with
two azido groups ((N<sub>3</sub>)<sub>2</sub>-(PBO-CCH)<sub>2</sub>), and (3) the intramolecular click cyclization of (N<sub>3</sub>)<sub>2</sub>-(PBO-CCH)<sub>2</sub> using the copper(I)
bromide/<i><i>N,N</i>,N′,N″,N″</i>-pentamethyldiethylenetriamine catalyst in DMF under high dilution
conditions. Size exclusion chromatography, FT-IR, and <sup>1</sup>H NMR measurements confirmed that the click reaction proceeded in
an intramolecular fashion to give 8-PBOs having <i>M</i><sub>n,NMR</sub>s ranging from ca. 3000 to 12 000 g mol<sup>–1</sup> and narrow <i>M</i><sub>w</sub>/<i>M</i><sub>n</sub>s of <1.06. The viscosity property of <i>s</i>-PBO and 8-PBO was evaluated together with linear and cyclic
PBOs (<i>l</i>-PBO and <i>c</i>-PBO, respectively).
The intrinsic viscosity ([η]) of <i>l</i>-PBO, <i>c</i>-PBO, <i>s</i>-PBO, and 8-PBO decreased in the
order of <i>l</i>-PBO > <i>s</i>-PBO > <i>c</i>-PBO > 8-PBO
Controlled/Living Ring-Opening Polymerization of Glycidylamine Derivatives Using <i>t</i>‑Bu‑P<sub>4</sub>/Alcohol Initiating System Leading to Polyethers with Pendant Primary, Secondary, and Tertiary Amino Groups
The combination of <i>t</i>-Bu-P<sub>4</sub> and alcohol
was found to be an excellent catalytic system for the controlled/living
ring-opening polymerization (ROP) of <i>N</i>,<i>N</i>-disubstituted glycidylamine derivatives, such as <i>N</i>,<i>N</i>-dibenzylglycidylamine (DBGA), <i>N</i>-benzyl-<i>N</i>-methylglycidylamine, <i>N</i>-glycidylmorpholine, and <i>N</i>,<i>N</i>-bis(2-methoxyethyl)glycidylamine,
to give well-defined polyethers having various pendant tertiary amino
groups with predictable molecular weights and narrow molecular weight
distributions (typically <i>M</i><sub>w</sub>/<i>M</i><sub>n</sub> < 1.2). The <i>t</i>-Bu-P<sub>4</sub>-catalyzed
ROP of these monomers in toluene at room temperature proceeded in
a living manner, which was confirmed by a MALDI-TOF MS analysis, kinetic
measurement, and postpolymerization experiment. The well-controlled
nature of the present system enabled the production of the block copolymers
composed of the glycidylamine monomers. The polyethers having pendant
primary and secondary amino groups, i.e., poly(glycidylamine) and
poly(glycidylmethylamine), respectively, were readily obtained by
the debenzylation of poly(DBGA) and poly(BMGA), respectively, through
the treatment with Pd/C in THF/MeOH under a hydrogen atmosphere. To
the best of our knowledge, this report is the first example of the
controlled/living polymerization of glycidylamine derivatives, providing
a rapid and comprehensive access to the polyethers having primary,
secondary, and tertiary amino groups
High-Performance Nonvolatile Organic Transistor Memory Devices Using the Electrets of Semiconducting Blends
Organic nonvolatile transistor memory
devices of the <i>n</i>-type semiconductor <i>N</i>,<i>N</i>′-bis(2-phenylethyl)-perylene-3,4:9,10-tetracarboxylic
diimide (BPE-PTCDI) were prepared using various electrets (i.e., three-armed
star-shaped poly[4-(diphenylamino)benzyl methacrylate] (N(PTPMA)<sub>3</sub>) and its blends with 6,6-phenyl-C<sub>61</sub>-butyric acid
methyl ester (PCBM), 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pen)
or ferrocene). In the device using the PCBM:N(PTPMA)<sub>3</sub> blend
electret,
it changed its memory feature from a write-once-read-many (WORM) type
to a flash type as the PCBM content increased and could be operated
repeatedly based on a tunneling process. The large shifts on the reversible
transfer curves and the hysteresis after implementing a gate bias
indicated the considerable charge storage in the electret layer. On
the other hand, the memory characteristics showed a flash type and
a WORM characteristic, respectively, using the donor/donor electrets
TIPS-pen:N(PTPMA)<sub>3</sub> and ferrocene:N(PTPMA)<sub>3</sub>.
The variation on the memory characteristics was attributed to the
difference of energy barrier at the interface when different types
of electret materials were employed. All the studied memory devices
exhibited a long retention over 10<sup>4</sup> s with a highly stable
read-out current. In addition, the afore-discussed memory devices
by inserting another electret layer of poly(methacrylic acid) (PMAA)
between the BPE-PTCDI layer and the semiconducting blend layer enhanced
the write-read-erase-read (WRER) operation cycle as high as 200 times.
This study suggested that the energy level and charge transfer in
the blend electret had a significant effect on tuning the characteristics
of nonvolatile transistor memory devices
Synthesis of α‑, ω‑, and α,ω-End-Functionalized Poly(<i>n</i>‑butyl acrylate)s by Organocatalytic Group Transfer Polymerization Using Functional Initiator and Terminator
The α-functionalized (hydroxyl,
ethynyl, vinyl, and norbornenyl),
ω-functionalized (ethynyl, vinyl, hydroxyl, and bromo), and
α,ω-functionalized polyacrylates were precisely synthesized
by the <i>N</i>-(trimethylsilyl)bis(trifluoroethanesulfonyl)imide
(Me<sub>3</sub>SiNTf<sub>2</sub>)-catalyzed group transfer polymerization
(GTP) of <i>n</i>-butyl acrylate (<i>n</i>BA).
The α-functionalization and ω-functionalization were carried
out using the functional triisopropylsilyl ketene acetal as the initiator
(initiation approach) and 2-phenyl acrylate derivatives as the terminator
(termination approach) for the organocatalytic GTP, respectively.
All the polymerizations precisely occurred and produced well-defined
end-functionalized poly(<i>n</i>-butyl acrylate)s which
had predictable molecular weights and narrow molecular weight distributions.
High-molecular-weight polyacrylates were easily synthesized using
both approaches. In addition, the α,ω-functionalized (hetero)telechelic
polyacrylates were synthesized by the combination of the initiation
and termination approaches. The structure of the obtained polyacrylates
and degree of functionalization were confirmed by the <sup>1</sup>H NMR and matrix-assisted laser desorption/ionization time-of-flight
mass spectroscopy (MALDI-TOF MS) measurements. The spectra of the <sup>1</sup>H NMR and MALDI-TOF MS showed that the end-functionalization
quantitatively proceeded without any side reactions