Enhancement of Tg of Poly(l‐lactide) by Incorporation of Biobased Mandelic‐Acid‐Derived Phenyl Groups by Polymerization and Polymer Blending

A high‐molecular‐weight polyester of poly(mandelate‐co‐lactate) (PML) is prepared by ring‐opening polymerization of stereo‐configuration controlled cyclic diester monomers of methyl‐6‐phenyl‐1,4‐dioxane‐2,5‐dione (MPDD) and lactide. The attained PML shows excellent glassy properties, although the original stereo‐configuration of MPDD is not preserved. The intrinsic high glass transition temperature (T_g) of PML is promising, and it is able to be further enhanced by thermal treatment to as high as 90 °C. Interestingly, the enhanced high T_g is attained by only 15 mol% of mandelate content in the polymer chain which is far lower than the ones suggested by theoretical calculation. The enhancement in T_g is also attained by polymer blending of PML and poly(l ‐lactide) (PLLA). The T_g of the polymer blend also reaches 90 °C which is almost 20 °C higher than the ones suggested by theoretical calculations. These results indicate that the rigid mandelate unit consisting of phenyl groups in PML chain effectively interact with PLLA chains in amorphous domain to restrict their chain mobility. The thermal and glassy properties are sufficient to explore new applications in engineering fields.     

Discharge Plasma Treatment as an Efficient Tool for Improved Poly(lactide) Adhesive–Wood Interactions

Poly(lactide) (PLA) films obtained by thermoforming or solution-casting were modified by diffuse coplanar surface barrier discharge plasma (300 W and 60 s). PLA films were used as hot-melt adhesive in joints in oak wood. It was demonstrated that lap shear strength increased from 3.4 to 8.2 MPa, respectively, for the untreated and plasma-treated series. Pull-off tests performed on particleboard for the untreated and treated PLA films showed 100% cohesive failure. Pull-off strength tests on solid oak demonstrated adhesion enhancement from 3.3 MPa with the adhesion failure mode to 6.6 MPa with the cohesion failure mode for untreated and treated PLA. XPS revealed that carbonyl oxygen content increased by two-to-three-fold, which was confirmed in the Fourier-transform infrared spectroscopy experiments of the treated PLA. The water contact angle decreased from 66.4° for the pristine PLA to 49.8° after treatment. Subsequently, the surface free energy increased from 47.9 to 61.05 mJ/m². Thus, it was clearly proven that discharge air plasma can be an efficient tool to change surface properties and to strengthen adhesive interactions between PLA and woody substrates.     

Fixation of horizontal maxillary osteotomies with biodegradable self-reinforced absorbable polylactide plates: preliminary results

Totally biodegradable, self-reinforced polylactide plates and titanium miniscrews were used for the fixation of horizontal maxillary osteotomies in 32 patients. In two cases the fixation was unstable because of technical problems. In the others the analysis of cephalometric radiographs between immediate and late postoperative showed very similar figures, indicating postoperative stability. There were no complications in the healing due to this biodegradable osteofixation in these patients.     

Hybrid Polypeptide/Polylactide Copolymers with Short Phenylalanine Blocks

Hybrid copolymers constituted by short l ‐phenylalanine (Phe) blocks (i.e., Phe_n with n ranging from 2 to 25) and l ‐lactide blocks of different length are synthesized and characterized. The diblock structure is obtained by ring opening polymerization of lactide using a Phe‐oligopeptide as macroinitiator. The length of the poly(l ‐lactide) (PLLA) block is controlled through the [lactide]/[macroinitiator] ratio. Morphologic studies of such hybrid copolymers indicate that the assembly of PLLA can be controlled by introducing short Phe blocks. Spherulites with both positive and negative birefringence are achieved in melt crystallization as a consequence of different lamellar distributions. Instead, a high variety of structures are detected in solution‐crystallized samples. Specifically, lozenge single crystals, flower‐like crystals, fibrillar structures, compact spheres, ringed sperulites, dendritic structures, microfibers, and braid‐like microstructures are observed. Some of the detected morphologies are characteristic of self‐assembled Phe‐oligopeptides, suggesting that Phe‐blocks play a crucial role in the self‐assembly properties.     

Synthesis and characterization of polycaprolactone / poly(ethylene oxide) / polylactide tri-component copolymers

Polycaprolactonel/poly(ethylene oxide)/polylactide tri-component copolymers (PCEL) with different compositions were synthesized by copolymerization of ε-caprolactone and L-lactide in the presence of poly(ethylene glycol) using stannous octoate as a catalyst. The copolymers were purified and characterized by various analytical techniques such as GPC, FT-IR, H NMR, ¹³C NMR, DSC, and X-ray diffractometry. It was evidenced that these copolymers were pure tri-component compounds which exhibited partially random chain structures, and possessed good mechanical properties and variable biodegradability.     

Selective Localization of Nanofillers: Effect on Morphology and Crystallization of PLA/PCL Blends

Adding nanofillers to PLA/PCL blends to change their surface and interface properties can improve their phase morphology. Here the selective localization of CNTs and organoclays as the third component in the blend is studied. It is found that clay is selectively localized in the PLA phase and at the phase interface whereas CNTs are mainly found in the PCL phase and at the phase interface. With a reduced viscosity ratio of the blend matrices, the CNTs change their preferred localization from PCL to PLA. The effects of the different selective localization of clay and CNTs on the morphologies are studied. In addition, the crystallization behavior of ternary systems also shows a strong dependence on the selective localization of nanofillers.

     

Biodegradation, soft and hard tissue integration of various polyethylene glycol hydrogels: a histomorphometric study in rabbits

Objectives: (i) To evaluate biodegradation, hard and soft tissue integration using various polyethylene glycol (PEG) hydrogels; (ii) to evaluate the influence of arginine–glycine–aspartic acid (RGD) on two types of PEG hydrogels. Material and methods: In seven rabbits, six treatment modalities were randomly applied subperiosteally on the skull: (1) a dense network PEG hydrogel (PEG1), (2) PEG1 modified with RGD (PEG1‐RGD), (3) a looser network PEG hydrogel (PEG2), (4) PEG2 modified with RGD (PEG2‐RGD), (5) a collagen membrane, and (6) a polylactide/polyglycolide/trimethylene carbonate membrane. The animals were sacrificed at 14 days. Histomorphometric analyses were performed on undecalcified Epon sections using a standardized region of interest. For statistical analysis, paired t‐test and signed rank test were applied. Results: PEG1 and PEG1‐RGD remained intact and maintained the shape. PEG2 and PEG2‐RGD completely degraded and were replaced by connective tissue and bone. The largest amount of mineralized tissue was found for PEG2‐RGD (21.4%), followed by PEG 2 (9.5%). The highest percentage of residual hydrogel/membrane was observed for PEG1‐RGD (55.6%), followed by PEG1 (26.7%). Conclusions: Modifications of the physico‐chemical properties of PEG hydrogels and the addition of RGD influenced soft and hard tissue integration and biodegradation. PEG1 showed an increased degradation time and maintained the shape. The soft tissue integration was enhanced by adding an RGD sequence. A high turn‐over rate and extensive bone regeneration was observed using PEG2. The addition of RGD further improved bone formation and soft tissue integration. To cite this article:
Thoma DS, Subramani K, Weber FE, Luder HU, Hämmerle CHF, Jung RE. Biodegradation, soft and hard tissue integration of various polyethylene glycol hydrogels: a histomorphometric study in rabbits.
Clin. Oral Impl. Res. 22 , 2011; 1247–1254.
doi: 10.1111/j.1600‐0501.2010.02075.x     

Modification and Properties of Cellulose Nonwoven Fabric—Multifunctional Mulching Material for Agricultural Applications

The paper describes a method of modifying a commercial viscose nonwoven fabric and its use as a modern mulching material in agriculture. The conducted research confirmed that the proposed modification of the viscose nonwoven fabric could be successfully used as a multipurpose and, above all, completely biodegradable nonwoven crop cover, which will eliminate the problem of disposal after the harvest period. Modified cellulose nonwoven fabric was obtained by staining with NB—BT helion brown, then padding with potassium nitrate (KNO₃) solution (used as a fertilizer) and finally coating with polylactide (PLA) solution. The characterisation of the nonwoven fabric included structural analysis, physicochemical properties and mechanical tests. The modified cellulose nonwovens were used in the tunnel cultivation of tomatoes as a heat-retardant, water-absorbing, antiweed mulching material that prevents soil infestation and slowly releases fertilizers.     

Polyethylenglycol-co-poly-D,L-lactide copolymer based microspheres: Preparation,characterization and delivery of a model protein

Purpose: To prepare and characterize polyethylenglycol-co-poly-D,L-lactide (PEG-D,L-PLA) multiblock copolymer microspheres containing ovalbumin. Microsphere batches made of Poly-D,L-lactide (PLA) homopolymers were prepared in order to evaluate how the presence of PEG segments into PEG-D,L-PLA copolymer could affect the behaviour of microspheres as carrier of protein drugs.

Methods: The PEG-D,L-PLA and PLA microspheres, loaded with the model protein ovalbumin, were prepared using double emulsion solvent evaporation method. The effect of PEG segments in the microparticles matrix, on the morphology, size distribution, encapsulation efficiency and release behaviour was studied.

Results: According to the results, PEG-D,L-PLA microspheres were more hydrophilic than PLA microparticles and with lower glass transition temperature. The surface of PEG-D,L-PLA microspheres was not as smooth as that of PLA microparticles, the mean diameter of PEG-D,L-PLA microparticles was bigger than that of PLA microspheres. Protein release from the microspheres was affected by the morphological structure of PEG-D,L-PLA microspheres and properties of PEG-D,L-PLA copolymer. This study suggests that PEG-D,L-PLA multiblock copolymer may be used as carrier in protein delivery systems for different purposes.     

生物可吸收张力带治疗尺骨茎突骨折的评价

背景：选择合适的内固定材料是治疗骨折成败的重要因素,生物可吸收材料成为骨折治疗的研究热点。目的：探讨生物可吸收张力带的材料特点以及治疗尺骨茎突骨折的疗效。方法：病例分析选取2009年11月至2012年2月采用生物可吸收张力带结合克氏针治疗尺骨茎突骨折患者36例,男21例,女15例;年龄21—73岁,平均年龄35．7岁,观察患者治疗后骨折愈合情况以及腕关节活动功能。并深入了解生物可吸收张力带材料种类和特性以及内固定的强度,比较生物可吸收张力带与金属张力带内固定的优缺点。结果与结论：生物可吸收张力带治疗尺骨茎突的36例患者,随访2个月-2．5年,平均随访8．5个月,X射线检查结果均提示骨折愈合,采用AO的Gartland．Werley方法对腕关节活动功能进行评估,优24例,良10例,中1例,差1例,优良率为94％。说明生物可吸收张力带有利于关节功能的恢复,在骨折愈合过程中可以逐渐转移应力,保持骨折部位的强度,材料的可降解性使患者避免了二次手术的痛苦。可见生物可吸收张力带结合克氏针治疗尺骨茎突骨折能取得较好的疗效。