PREPARATION AND CHARACTERIZATION OF INCLUSION COMPLEXES OF TWO-ARM LINEAR AND FOUR-ARM STAR-SHAPED POLY(ε-CAPROLACTONE)S WITH α-CYCLODEXTRIN

Both four-arm star-shaped poly(ε-caprolactone) (4sPCL) and two-arm linear PCL (2LPCL) were synthesized and their inclusion complexation with α-cyclodextrin (α-CD) were studied. The inclusion complexes (ICs) formed between the PCL polymers and α-CD were characterized by 1H-NMR, DSC, TGA, WAXD, and FT-IR, respectively. Both branch arm number and molecular weight of the PCL polymers have apparent effect on the stoichiometry (CL:CD, mol:mol) of these ICs. All these analytical results indicate that the branch arms of the PCL polymers are incorporated into the hydrophobicα-CD cavities and their original crystalline properties are completely suppressed. Moreover, the inclusion complexation between two-arm linear or four-arm star-shaped PCL polymers and α-CD not only enhances the thermal stability of the guest PCL polymers but also improves that of α-CD.     

Effect of Temperature-responsive Solution Behavior of PNIPAM-bPPEOMA-b-PNIPAM on Its Inclusion Complexation with α-Cyclodextrin

The effect of temperature-responsive solution behavior of PNIPAM-b-PPEOMA-b-PNIPAM on its inclusion complexation with α-cyclodextrin was studied. The triblock polymer was prepared by reversible addition-fragmentation chain transfer(RAFT) polymerization and formed inclusion complexes(ICs) after selective threading of the PEO segment of the triblock polymer through the cavities of α-CD units. For comparison, PPEOMA homopolymer was prepared and the inclusion complexation with α-CD was also studied. The ICs were prepared with α-CD when the polymer was in different conformations by changing the temperature, and the formed ICs were characterized by XRD, 1H-NMR, TGA and DSC. The solutions of the ICs show temperature-responsive clear/turbid transition or fluidic emulsion/gel transition depending on the concentration of the α-CD added, and the stoichiometry determined by 1H-NMR and TGA indicates that the stoichiometry of EO to α-CD of the resulted ICs increases with increasing of temperature.     

PREPARATION AND CHARACTERIZATION OF SHISH-KEBAB TYPE LIQUID CRYSTALLINE POLY（p-PHENYLENEVINYLENE）

Novel shish-kebab type liquid crystalline poly（p-phenylenevinylene） derivatives were synthesized by Stille coupling reaction from 2,5-bis[（4-n-alkoxyl）benzoyloxy]1,4-dibromobenzene （monomer l） and 1,2-bis（tributylstannyl） ethylene （monomer 2）. The polymers with alkoxy groups are soluble in common organic solvents and exhibit blue fluorescence. Both the cast film and the annealed film have large red-shifts in fluorescence spectra and show yellow fluorescence. The polymers with CN and NO2 groups show poor solubility and green fluorescence. All the polymers possess liquid crystalline smectic phases. The melting point （Tm） of the polymers decreases when the length of the alkoxy tails of the mesogenic units increases. The polymers are easily aligned under a magnetic field of 10 Tesla. It is found that the conjugated backbone and LC side chain are aligned perpendicular and parallel to the magnetic field, respectively. The polymers show optical dichroism in fluorescence spectra, suggesting that they are available for advance materials with linear optical polarization.     

Solution Crystallization Behavior of Linear and Star-shaped Poly(ethylene glycol)-b-Poly(ε-caprolactone) Block Copolymers简

Lamellar crystals of diblock, triblock and four-arm poly（ethylene glycol）-b-poly（ε-caprolactone） （PEG-b-PCL） crystalline-crystalline copolymers were successfully obtained from their solution. Morphology and structure of lamellar crystals of crystalline-crystalline copotymers were investigated using tapping-mode atomic force microscopy （AFM） and selected area electron diffraction （SAED）. All of these samples showed the truncated-lozenge multilayer basal shapes with central screw dislocation or central stack, which were all obtained simultaneously from the oil bath. The diffraction pattern of PEG block lamellar crystal is attributed to the （120） diffracting planes and the pattern of PCL block lamellar crystal is attributed to the （1 I0） diffracting planes and （200） diffracting planes according to the SAED results. Four （110） crystal growth planes and two （200） crystal growth planes are discovered for the PCL blocks, but the （120） crystal growth planes of PEG blocks are hided in the figure of AFM. The crystalline structure of the four-arm copolymers （FA） is more disorder and confused than that of the diblock （DI） copolymer and the striated fold surface structures of lamellar crystals of four-arm copolymers （FA） are smoother than these of linear analogues, owing to the confused crystallization of blocks caused by the mutual restriction of blocks and the hindrance of the dendritic cores. In addition, the aspect ratio of FA is greater than that of the others. It is hypothesized that there are two reasons for the change of aspect ratios. First, the （200） diffracting planes of PCL crystals grew slowly compared to their （110） diffracting planes because of difference in the energy barrier. Secondly, edge dislocations on the （200） diffracting planes are also responsible for the variation of the aspect ratio. Consequently, the crystalline defects are augmented by the competing blocks crystallized simultaneously and the hindrance of the dendritic cores.     

Spectroscopic Study on Interaction of β-Cyclodextrin with Triprolidine Hydrochloride

The complexation of triprolidine hydrochloride （TRP） and β-cyclodextrin （β-CD） in deuterium oxide was investigated by 400 MHz 1^H NMR spectroscopy. The 800 MHz 2D ROESY data revealed that two 1 ：1 and one 2 ： 1 β-CD-TRP inclusion complexes were formed. Both aromatic moieties （p-tolyl and pyridyl ring） has entered into the β-CD cavity, confirming the existence of two different equilibria for 1 ： 1 inclusion complexes in which p-tolyl ring of the guest is more tightly held by the host cavity. The ROE intermolecular interactions provided the plausible structures of these 1 ： 1 and 2 ： 1 stoichiometric inclusion complexes of β-CD-triprolidine hydrochloride in solu- tion.     

SYNTHESIS AND PROPERITIES OF SHISH-KEBAB-TYPE LIQUID CRYSTALLINE POLY（p-PHENYLENE）S

Abstract The novel shish-kebab-type liquid crystalline poly（p-phenylene）s were synthesized through Suzuki coupling reaction from 2,5-bis[（4-n-alkoxyl）benzoyloxy]1,4-dibromobenzene （monomer 1） and 1,4-benzenediboronic acid bistrimethylene cyclic ester （monomer 2）. Their structure and properties were characterized by GPC, DSC, X-ray diffraction and polarizing optical microscope （POM）. It was found that the polymers turned to liquid crystalline phase above their melting point. The melting point （Tm） of the polymers decreases when the length of the alkoxy tails of the mesogenic units increases. The mesophase was identified by X-ray diffraction method. The polymers could dissolve in common organic solvents and show strong blue fluorescence. The maximum absorption bands of polymers prepared from annealed films have large red-shift due to the spontaneous orientation of the liquid crystalline side chains. The same phenomena were also observed in the fluorescence spectra.     

A MORPHOLOGICAL STUDY OF POLY（DIVINYLBENZENE-co-ACRYLIC ACID） IN CROSSLINKING PRECIPITATION POLYMERIZATION

Divinylbenzene-80 （DVB-80） and polar monomer acrylic acid （AA） having hydrogen bonding at a total monomer loading of 5 vol% were precipitated-copolymerized in a variety of organic solvents with 2,2＇-azobis（isobutyronitrile） （AIBN） as initiator. The experiments were investigated from a two-dimensional matrix, i.e., the actual crosslinking degree of DVB varying from 0 to 80% and the solvent composition varying from 0 to 100% of toluene mixture with acetonitrile, when the mixture of acetonitrile and toluene was used as the reaction solvent. Under various reaction conditions, six distinct morphologies including soluble polymers, swellable microgels, coagulum, irregular microparticles, and nano-/micrometer microspheres were formed and the structures of these polymer architectures were described. A morphological map was utilized to discuss the effects of both crosslinking degree of DVB and composition of solvent on the transitions between morphology domains. The results demonstrated that the microspheres are formed by an internal contraction due to the marginal solvency of the continuous phase and the crosslinking of the polymer network through the covalent bonding from DVB as well as the interchain hydrogen-bonding between the carboxylic acid units.     

SYNTHESIS OF CHIRAL CONJUGATED POLYBINAPHTHYLS BY SONOGASHIRA REACTION

Chiral polymers P-1 and P-2 were synthesized by the polymerization of （R）-3,3＇-diiodo-2,2＇-bisbutoxy-1,1＇- binaphthyl （M- 1 ） with 2,5-di（4-ethynylphenyl）- 1,3,4-oxadiazole （M-3） and （R）-3,3＇-diethylnyl-2,2＇-bisbutoxy- 1,1 ＇-binaphthyl （M-2） with 1,2-di（4-bromophenyl）acetylene （M-4） under Sonogashira reaction, respectively. Both monomers and polymers were analyzed by NMR, MS, FT-IR, UV-Vis spectroscopy, DSC-TGA, fluorescence spectroscopy, GPC and CD spectroscopy. CD spectra of P-1 and P-2 are similar due to the same chiral center units and main chain structure. The long wavelengths CD effect of P-1 and P-2 can be regarded as the more extended conjugated structure and a highly rigid backbone in the polymer chain. Polymers have strong blue fluorescence due to the efficient energy migration from the extended n-electronic structure of the polymers to the chiral binaphthyl core and are expected to provide understanding of the relationship between molecular structure and fluorescent property of the chiral polymers.     

MOLECULAR DESIGN OF FUNCTIONAL POLYMERS BASED ON UNIQUE PROPERTIES OF POLYMER CHAINS

The inclusion complex formation of α-CD, β-CD, and γ-CD with various water-soluble polymers has beeninvestigated, and the relationship between the chain cross-sectional areas of the polymers and the diameters of the cavities ofcyclodextrins (molecular recognition) was found. Polyrotaxanes and tubular polymers were prepared on the basis ofmolecular recognition. Several kinds of polymers having tetraphenylporphyrin (TPP) and paramagnetic metallotetraphenyl-porphyrin (AgTPP, CuTPP, VOTPP or ZnTPP) have been prepared by radical polymerization of the correspondingmonomers. Visible spectra of these polymers show hypochromism in the Sorer bands of TPP moieties as compared withthose of monomers. Polymer effects were observed in the magnetic behavior and oxygen adsorption of paramagneticmetallotetraphenylporphyrin moieties. Moreover, polymer effects on photophysical and photochemical behavior were foundin the amphiphilic polymers covalently tethered with small amounts of zinc(Ⅱ)-tetraphenylporphyrin (ZnTPP).     

PREPARATION AND CHARACTERIZATION OF PVDF-HFP MICROPOROUS MEMBRANE BY TEMPLATE METHOD

Porous poly（vinylidene fluoride-co-hexafluoropropylene） （PVDF-HFP） membranes were successfully prepared using dibutyl phthalate （DBP）, polyvinylpyrrolidone （PVP-K30）, polyethylene glycol 200 （PEG200） as templates. SEM was used to examine the morphology of the PVDF-HFP porous membranes. It was found that these membranes have an asymmetric structure and the blends of PVDF-HFP/DBP formed nanoporous membranes, whereas the blends of PVDF- HFP/PVP-K30 formed ＂sponge-like＂ and microporous membranes. Moreover, the average pore size and porosity was about 0.3 μm and 48.7%, respectively. The crystallinity, thermal stability and mechanical strength of membranes were characterized by XRD, DSC, TGA and stress-strain tests. The results showed that the membranes are a crystals with excellent thermal stability. It was an effective way to regulate pore size and morphology of the PVDF-HFP membranes.     

Supramolecular inclusion complexes of star‐shaped poly(ε‐caprolactone) with α‐cyclodextrin

Both star‐shaped poly(ε‐caprolactone) (PCL) having 4 arms (4sPCL) and 6 arms (6sPCL) and linear PCL having 1 arm (LPCL) and 2 arms (2LPCL) were synthesized and then investigated for inclusion complexation with α‐cyclodextrin (α‐CD). The supramolecular inclusion complexes (ICs) were in detail characterized by ¹H NMR, differential scanning calorimetry, thermogravimetric analysis, wide angle X‐ray diffraction, solid‐state carbon nuclear magnetic resonance spectroscopy using cross‐polarization and magic‐angle spinning, and Fourier transform infrared, respectively. The stoichiometry (CL:CD, mol:mol) of all ICs increased with the increasing branch arm of PCL polymers, and it was in the order of α‐CD‐6sPCL1 ICs > α‐CD‐4sPCL ICs > α‐CD‐2LPCL ICs > α‐CD‐LPCL ICs. All analyses indicated that the branch arms of star‐shaped PCL polymers were included into the hydrophobic α‐CD cavities and their original crystalline properties were completely suppressed. Moreover, the ICs of star‐shaped PCL with α‐CD had a channel‐type crystalline structure similar to that formed between the linear PCL and α‐CD. Furthermore, the thermal stability of the free PCL polymers probably controlled that of the guest polymers included in the ICs. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4721–4730, 2005     

Supramolecular inclusion complexation of polyhedral oligomeric silsesquioxane capped poly(ε‐caprolactone) with α‐cyclodextrin

Supramolecular inclusion complexes (ICs) involving polyhedral oligomeric silsesquioxane (POSS) capped poly(?‐caprolactone) (PCL) and α‐cyclodextrin (α‐CD) were investigated. POSS‐terminated PCLs with various molecular weights were prepared via the ring‐opening polymerization of ?‐caprolactone (CL) with 3‐hydroxypropylheptaphenyl POSS as an initiator. Because of the presence of the bulky silsesquioxane terminal group, the inclusion complexation between α‐CD and the POSS‐capped PCL was carried out only with a single end of a PCL chain threading inside the cavity of α‐CD, which allowed the evaluation of the effect of the POSS terminal groups on the efficiency of the inclusion complexation. The X‐ray diffraction results indicated that the organic–inorganic ICs had a channel‐type crystalline structure. The stoichiometry of the organic–inorganic ICs was quite dependent on the molecular weights of the POSS‐capped PCLs. With moderate molecular weights of the POSS‐capped PCLs (e.g., M_n =3860 or 9880), the stoichiometry was 1:1 mol/mol (CL unit/α‐CD), which was close to the literature value based on the inclusion complexation of α‐CD with normal linear PCL chains with comparable molecular weights. When the PCL chains were shorter (e.g., for the POSS‐capped PCL of M_n = 1720 or 2490), the efficiency of the inclusion complexation decreased. The decreased efficiency of the inclusion complexation could be attributed to the lower mobility of the bulky POSS group, which restricted the motion of the PCL chain attached to the silsesquioxane cage. This effect was pronounced with the decreasing length of the PCL chains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1247–1259, 2007     

Organic–inorganic hybrid brushes consisting of macrocyclic oligomeric silsesquioxane and poly(ε‐caprolactone): Synthesis,characterization, and supramolecular inclusion complexation with α‐cyclodextrin

Organic–inorganic hybrid brushes comprised of macrocyclic oligomeric silsesquioxane (MOSS) and poly(ε‐caprolactone) (PCL) were synthesized via the ring‐opening polymerization of ε‐caprolactone (CL) with cis‐hexa[(phenyl) (2‐hydroxyethylthioethyldimethylsiloxy)]cyclohexasiloxane as the initiator. The MOSS macromer bearing hydroxyl groups was synthesized via the thiol‐ene radical addition reaction between cis‐hexa[(phenyl)(vinyldimethylsiloxy)]cyclohexasiloxane and β‐mercaptoethanol. The organic–inorganic PCL cyclic brushes were characterized by means of nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). These MOSS–PCL brushes were then used to prepare the supramolecular inclusion complexes with α‐cyclodextrin (α‐CD). The X‐ray diffraction (XRD) indicates that the organic–inorganic inclusion complexes (ICs) have a channel‐type crystalline structure. It is noted that the molar ratios of CL unit to α‐CD for the organic–inorganic ICs are quite dependent on the lengths of the PCL chains bonded to the silsesquioxane macrocycle. While the PCL chains were short, the efficiency of inclusion complexation was significantly decreased. The decreased efficiency could be attributed to the repulsion of the adjacent PCL chains bonded to the silsesquioxane macrocycle and the restriction of the bulky silsesquioxane macrocycle on the motion of PCL chains; this effect is pronounced with decreasing the length of the PCL chains. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Effects of multi-arm structure on crystallization and biodegradation of star-shaped poly(epsilon-caprolactone)

Star-shaped PCL with one to five arms were synthesized by ROP. They have the same crystal structure as linear PCL, indicating that the central cores are located in amorphous regions. The influence of arm length and number on crystallization and melting behavior were studied by DSC, POM, and through the Avrami equation. A model is proposed to analyze the enzymatic degradation process of star-shaped polymers. The multi-arm structure and the limitation of the central cores on the chain mobility of each arm are considered to be the primary factors influencing the characteristic crystallization and enzymatic degradation behavior of star-shaped PCLs.     

Synthesis and Characterization of Four-Arm Star Poly(ϵ-caprolactone)-Block-Poly(cyclic-carbonate methacrylate) Copolymers by Combining Ring-Opening Polymerization With Atom Transfer Radical Polymerization

Well-defined four-arm star poly(?-caprolactone)-block-poly(cyclic carbonate methacrylate) (PCL-b-PCCMA) copolymers were synthesized by combining ring-opening polymerization (ROP) with atom transfer radical polymerization (ATRP). First, a four-arm poly(?-caprolactone) (PCL) macroinitiator [(PCL-Br)₄] was prepared by the ROP of ?-CL catalyzed by stannous octoate at 110°C in the presence of pentaerythritol as the tetrafunctional initiator followed by esterification with 2-bromoisobutyryl bromide. The sequential ATRP of CCMA monomer was carried out by using the (PCL-Br)₄ tetrafunctional macroinitiator (MI) and in the presence of CuBr/2, 2′-bipyridyl system in DMF at 80°C with [(MI)]:[CuBr]:[bipyridyl] = 1:1:3 to yield block polymers with controlled molecular weights (M_n (NMR) = 10700 to 27300 g/mol) by varying block lengths and with moderately narrow polydispersities (M_w/M_n = 1.2–1.4). Block copolymers with different PCL: PCCMA copolymer composition such as 50:50, 70:30 and 74:26 were prepared with good yields (48-74%). All these block copolymers were well characterized by NMR, FTIR and GPC and tested their thermal properties by DSC and TGA.     

Supramolecular aggregations through the inclusion complexation of cyclodextrins and polymers with bulky end groups

Mono‐polyhedral oligomeric sillsesquioxane‐end capped poly(ε‐caprolactone) (mPPCL) can form inclusion complexes (ICs) with α‐ and γ‐cyclodextrins (CDs) but not with β‐CD. These CD ICs have been characterized with X‐ray diffraction, solid‐state ¹³C cross‐polarization/magic‐angle‐spinning NMR spectroscopy, ¹H NMR spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and scanning electron microscopy. The poly(ε‐caprolactone) (PCL) chain of mPPCL is included within the channel provided by the CDs to form a columnar, crystalline structure. The PCL/CD ratios determined by ¹H NMR spectroscopy for the ICs with α‐ or γ‐CDs are higher than the stoichiometries because of the steric hindrance of the bulky polyhedral oligomeric silsesquioxane chain end and result in a fraction of the ε‐caprolactone units free from complexation with the CDs. On the basis of these analyses, we propose some possible structures for these CD/mPPCL ICs. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 125–135, 2007     

POSS end‐linked peptide‐functionalized poly(ɛ‐caprolactone)s and their inclusion complexes with α‐cyclodextrin

In this report, we have synthesized organic/inorganic hybrid peptide–poly(?‐caprolactone) (PCL) conjugates via ring opening polymerization (ROP) of ?‐caprolactone (CL) in the presence of two sequence defined peptide initiators, namely POSS‐Leu‐Aib‐Leu‐NH₂ (POSS: polyhedral oligomeric silsesquioxane; Leu: Leucine; Aib: α‐aminoisobutyric acid) and OMe‐Leu‐Aib‐Leu‐NH₂. Covalent attachment of peptide segments with the PCLs were examined by ¹H and ²⁹Si NMR spectroscopy, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) and FTIR spectroscopy. Supramolecular inclusion complexations of synthesized peptide‐PCL conjugates with α‐cyclodextrin (α‐CyD) were studied to understand the effect of POSS/OMe‐peptide moieties at the PCL chain ends. Inclusion complexation of peptide‐PCL conjugates with α‐CyD produced linear polypseudorotaxane, confirmed by ¹H NMR, FTIR, powder X‐ray diffraction (PXRD), polarized optical microscopy (POM) and differential scanning calorimetry (DSC). Extent of α‐CyD threading onto the hybrid peptide‐PCL conjugated polymers is less than that of α‐CyD threaded onto the linear PCL. Thus, PCL chains were not fully covered by the host α‐CyD molecules due to the bulky POSS/OMe‐peptide moieties connected with the one edge of the PCL chains. PXRD experiment reveals channel like structures by the synthesized inclusion complexes (ICs). Spherulitic morphologies of POSS/OMe‐peptide‐PCL conjugates were fully destroyed after inclusion complexation with α‐CyD and tiny nanoobjects were produced. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3643–3651.     

Biodegradable and biocompatible inorganic–organic hybrid materials. I. Synthesis and characterization

The hydroxyl or vinyl end-groups of linear or three-arm star-shaped poly(ε-caprolactone) (PCL) chains have been derivatized into triethoxysilane groups reactive in the sol-gel process. New transparent hybrid materials that combine tetraethylorthosilicate (TEOS) and PCL known for biodegradability and biocompatibility have accordingly been prepared. The sol-gel process is, however, limited by the early vitrification of the reactive system. However, thermal posttreatment can overcome these diffusional and/or kinetic limitations as assessed by a set of analytical methods. The thermal stability of PCL is improved by incorporation into the silica network. Conversely, the thermal stability of the ceramer depends on the effective PCL content. The extent of PCL incorporation into the silica network depends on PCL molecular weight, number, and reactivity of the PCL functional groups. IR spectroscopy has shown that hydrogen bonding occurs between the ester groups of PCL and residual OH groups of the silicate component. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2295–2309, 1997     

Studies on Molecular Recongnition of (a)-Cyclodextrin with Diphenyl compounds

The cyclodextrins(CDs) are a class of cyclic oligosaccharides made up of six(a), seven(a)or more [a-(1,4)-linked] D-glucopyranose units, and shaped like truncated cones with primary and secondary hydroxyl groups crowning the narrower rim and wider rim respectively. As they have a hydrophobic cavity of appropriate dimension, they can bind with various guest moleculars, such as hydrocarbon, cyclohexane, aromatic compounds, to form inclusion complexes. The cyclodextins inclusion complexation has been considered an ideal model mimicking the enzyme-substrate interaction and a lot of effect has been devoted to it. In this paper, we report our investigation on the inclusion complexation behavior of a-cyclodextrin(a-CD) with diphenyl compounds in order to further explore the molecular recongnition mechanism of 2:1 inclusion complexation of a-CD with aromatic compounds.Figure 1: Possible structures of the inclusion compounds.The inclusion complexation behavior of a-CD with sym-diphenyl-urea, sym-diphenyl-thiourea and diphenyl kotone as respective guest moleclars was studied by ultraviolet spectrometric titrations.The absorption spectral changes observed for the compounds in the absence and presence of a-CD are used to draw the corresponding Benesi-Hildebrand plots and caculate the complex stability constant value (Ks) for the inclusion compounds.The 2:1 inclusion complexations show higher binding constants by cooperative binding of one guest molecular in the closely two hydrophobic cyclodextrin cavites as compared with 1:1 inclusion complexations.The highest value observed for sym-diphenyl-urea could be due to the formation of a hydrogen bond between the carbonyl group and the hydrogen in the hydroxyl group of CD and this is not possible with sym-tiphenyl-thiourea. The lowest value observed for diphenyl kotone indicate the hydrophobic interaction is one of the binding force of cyclodextrin inclusion complex.     

Porous thin films based on photo-cross-linked star-shaped poly(D,L-lactide)s

Self-assembly processes and subsequent photo-cross-linking were used to generate cross-linked, ordered microporous structures on the surfaces of well defined four-arm star-shaped poly(D,L-lactide) (PDLLA) thin films. The four-arm star-shaped PDLLAs were synthesized using an ethoxylated pentaerythritol initiator. Solutions of the PDLLAs were cast in a humid environment, and upon solvent evaporation, ordered honeycomb structures (or breath figures) were obtained. Correlations between molar mass, polymer solution viscosity, and pore dimensions were established. The average pore dimension decreased with increasing polymer solution concentration, and a linear relationship was observed between relative humidity and average pore dimensions. Highly ordered microporous structures were also developed on four-arm star-shaped methacrylate-modified PDLLA (PDLLA-UM) thin films. Subsequent photo-cross-linking resulted in more stable PDLLA porous films. The photo-cross-linked films were insoluble, and the honeycomb structures were retained despite solvent exposure. Free-standing, structured PDLLA-UM thin films were obtained upon drying for 24 h. Ordered microporous films based on biocompatible and biodegradable polymers, such as PDLLA, offer potential applications in biosensing and biomedical applications.